INTEGER ALGORITHMS TO SOLVE LINEAR EQUATIONS AND SYSTEMS

Download INTEGER ALGORITHMS TO SOLVE LINEAR EQUATIONS AND SYSTEMS PDF Online Free

Author :
Publisher : Infinite Study
ISBN 13 :
Total Pages : 120 pages
Book Rating : 4./5 ( download)

DOWNLOAD NOW!


Book Synopsis INTEGER ALGORITHMS TO SOLVE LINEAR EQUATIONS AND SYSTEMS by : Florentin Smarandache

Download or read book INTEGER ALGORITHMS TO SOLVE LINEAR EQUATIONS AND SYSTEMS written by Florentin Smarandache and published by Infinite Study. This book was released on with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Original integer general solutions, together with examples, are presented to solve linear equations and systems.

ANOTHER INTEGER NUMBER ALGORITHM TO SOLVE LINEAR EQUATIONS (USING CONGRUENCY)

Download ANOTHER INTEGER NUMBER ALGORITHM TO SOLVE LINEAR EQUATIONS (USING CONGRUENCY) PDF Online Free

Author :
Publisher : Infinite Study
ISBN 13 :
Total Pages : 7 pages
Book Rating : 4./5 ( download)

DOWNLOAD NOW!


Book Synopsis ANOTHER INTEGER NUMBER ALGORITHM TO SOLVE LINEAR EQUATIONS (USING CONGRUENCY) by : Florentin Smarandache

Download or read book ANOTHER INTEGER NUMBER ALGORITHM TO SOLVE LINEAR EQUATIONS (USING CONGRUENCY) written by Florentin Smarandache and published by Infinite Study. This book was released on with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this section is presented a new integer number algorithm for linear equation. This algorithm is more “rapid” than W. Sierpinski’s presented in in the sense that it reaches the general solution after a smaller number of iterations. Its correctness will be thoroughly demonstrated.

Collected Papers, Vol. I

Download Collected Papers, Vol. I PDF Online Free

Author :
Publisher : Infinite Study
ISBN 13 : 973920502X
Total Pages : 305 pages
Book Rating : 4.7/5 (392 download)

DOWNLOAD NOW!


Book Synopsis Collected Papers, Vol. I by : Florentin Smarandache

Download or read book Collected Papers, Vol. I written by Florentin Smarandache and published by Infinite Study. This book was released on 1996 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Discrete Mathematics

Download Discrete Mathematics PDF Online Free

Author :
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781534970748
Total Pages : 342 pages
Book Rating : 4.9/5 (77 download)

DOWNLOAD NOW!


Book Synopsis Discrete Mathematics by : Oscar Levin

Download or read book Discrete Mathematics written by Oscar Levin and published by Createspace Independent Publishing Platform. This book was released on 2016-08-16 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: This gentle introduction to discrete mathematics is written for first and second year math majors, especially those who intend to teach. The text began as a set of lecture notes for the discrete mathematics course at the University of Northern Colorado. This course serves both as an introduction to topics in discrete math and as the "introduction to proof" course for math majors. The course is usually taught with a large amount of student inquiry, and this text is written to help facilitate this. Four main topics are covered: counting, sequences, logic, and graph theory. Along the way proofs are introduced, including proofs by contradiction, proofs by induction, and combinatorial proofs. The book contains over 360 exercises, including 230 with solutions and 130 more involved problems suitable for homework. There are also Investigate! activities throughout the text to support active, inquiry based learning. While there are many fine discrete math textbooks available, this text has the following advantages: It is written to be used in an inquiry rich course. It is written to be used in a course for future math teachers. It is open source, with low cost print editions and free electronic editions.

Methods of Solving Number Theory Problems

Download Methods of Solving Number Theory Problems PDF Online Free

Author :
Publisher : Birkhäuser
ISBN 13 : 3319909150
Total Pages : 405 pages
Book Rating : 4.3/5 (199 download)

DOWNLOAD NOW!


Book Synopsis Methods of Solving Number Theory Problems by : Ellina Grigorieva

Download or read book Methods of Solving Number Theory Problems written by Ellina Grigorieva and published by Birkhäuser. This book was released on 2018-07-06 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt: Through its engaging and unusual problems, this book demonstrates methods of reasoning necessary for learning number theory. Every technique is followed by problems (as well as detailed hints and solutions) that apply theorems immediately, so readers can solve a variety of abstract problems in a systematic, creative manner. New solutions often require the ingenious use of earlier mathematical concepts - not the memorization of formulas and facts. Questions also often permit experimental numeric validation or visual interpretation to encourage the combined use of deductive and intuitive thinking. The first chapter starts with simple topics like even and odd numbers, divisibility, and prime numbers and helps the reader to solve quite complex, Olympiad-type problems right away. It also covers properties of the perfect, amicable, and figurate numbers and introduces congruence. The next chapter begins with the Euclidean algorithm, explores the representations of integer numbers in different bases, and examines continued fractions, quadratic irrationalities, and the Lagrange Theorem. The last section of Chapter Two is an exploration of different methods of proofs. The third chapter is dedicated to solving Diophantine linear and nonlinear equations and includes different methods of solving Fermat’s (Pell’s) equations. It also covers Fermat’s factorization techniques and methods of solving challenging problems involving exponent and factorials. Chapter Four reviews the Pythagorean triple and quadruple and emphasizes their connection with geometry, trigonometry, algebraic geometry, and stereographic projection. A special case of Waring’s problem as a representation of a number by the sum of the squares or cubes of other numbers is covered, as well as quadratic residuals, Legendre and Jacobi symbols, and interesting word problems related to the properties of numbers. Appendices provide a historic overview of number theory and its main developments from the ancient cultures in Greece, Babylon, and Egypt to the modern day. Drawing from cases collected by an accomplished female mathematician, Methods in Solving Number Theory Problems is designed as a self-study guide or supplementary textbook for a one-semester course in introductory number theory. It can also be used to prepare for mathematical Olympiads. Elementary algebra, arithmetic and some calculus knowledge are the only prerequisites. Number theory gives precise proofs and theorems of an irreproachable rigor and sharpens analytical thinking, which makes this book perfect for anyone looking to build their mathematical confidence.

Elementary Number Theory: Primes, Congruences, and Secrets

Download Elementary Number Theory: Primes, Congruences, and Secrets PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 0387855254
Total Pages : 173 pages
Book Rating : 4.3/5 (878 download)

DOWNLOAD NOW!


Book Synopsis Elementary Number Theory: Primes, Congruences, and Secrets by : William Stein

Download or read book Elementary Number Theory: Primes, Congruences, and Secrets written by William Stein and published by Springer Science & Business Media. This book was released on 2008-10-28 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a book about prime numbers, congruences, secret messages, and elliptic curves that you can read cover to cover. It grew out of undergr- uate courses that the author taught at Harvard, UC San Diego, and the University of Washington. The systematic study of number theory was initiated around 300B. C. when Euclid proved that there are in?nitely many prime numbers, and also cleverly deduced the fundamental theorem of arithmetic, which asserts that every positive integer factors uniquely as a product of primes. Over a thousand years later (around 972A. D. ) Arab mathematicians formulated the congruent number problem that asks for a way to decide whether or not a given positive integer n is the area of a right triangle, all three of whose sides are rational numbers. Then another thousand years later (in 1976), Di?e and Hellman introduced the ?rst ever public-key cryptosystem, which enabled two people to communicate secretely over a public communications channel with no predetermined secret; this invention and the ones that followed it revolutionized the world of digital communication. In the 1980s and 1990s, elliptic curves revolutionized number theory, providing striking new insights into the congruent number problem, primality testing, publ- key cryptography, attacks on public-key systems, and playing a central role in Andrew Wiles’ resolution of Fermat’s Last Theorem.

Theory of Linear and Integer Programming

Download Theory of Linear and Integer Programming PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 9780471982326
Total Pages : 488 pages
Book Rating : 4.9/5 (823 download)

DOWNLOAD NOW!


Book Synopsis Theory of Linear and Integer Programming by : Alexander Schrijver

Download or read book Theory of Linear and Integer Programming written by Alexander Schrijver and published by John Wiley & Sons. This book was released on 1998-06-11 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theory of Linear and Integer Programming Alexander Schrijver Centrum voor Wiskunde en Informatica, Amsterdam, The Netherlands This book describes the theory of linear and integer programming and surveys the algorithms for linear and integer programming problems, focusing on complexity analysis. It aims at complementing the more practically oriented books in this field. A special feature is the author's coverage of important recent developments in linear and integer programming. Applications to combinatorial optimization are given, and the author also includes extensive historical surveys and bibliographies. The book is intended for graduate students and researchers in operations research, mathematics and computer science. It will also be of interest to mathematical historians. Contents 1 Introduction and preliminaries; 2 Problems, algorithms, and complexity; 3 Linear algebra and complexity; 4 Theory of lattices and linear diophantine equations; 5 Algorithms for linear diophantine equations; 6 Diophantine approximation and basis reduction; 7 Fundamental concepts and results on polyhedra, linear inequalities, and linear programming; 8 The structure of polyhedra; 9 Polarity, and blocking and anti-blocking polyhedra; 10 Sizes and the theoretical complexity of linear inequalities and linear programming; 11 The simplex method; 12 Primal-dual, elimination, and relaxation methods; 13 Khachiyan's method for linear programming; 14 The ellipsoid method for polyhedra more generally; 15 Further polynomiality results in linear programming; 16 Introduction to integer linear programming; 17 Estimates in integer linear programming; 18 The complexity of integer linear programming; 19 Totally unimodular matrices: fundamental properties and examples; 20 Recognizing total unimodularity; 21 Further theory related to total unimodularity; 22 Integral polyhedra and total dual integrality; 23 Cutting planes; 24 Further methods in integer linear programming; Historical and further notes on integer linear programming; References; Notation index; Author index; Subject index

Quadratic Number Theory

Download Quadratic Number Theory PDF Online Free

Author :
Publisher : American Mathematical Soc.
ISBN 13 : 1470447371
Total Pages : 410 pages
Book Rating : 4.4/5 (74 download)

DOWNLOAD NOW!


Book Synopsis Quadratic Number Theory by : J. L. Lehman

Download or read book Quadratic Number Theory written by J. L. Lehman and published by American Mathematical Soc.. This book was released on 2019-02-13 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quadratic Number Theory is an introduction to algebraic number theory for readers with a moderate knowledge of elementary number theory and some familiarity with the terminology of abstract algebra. By restricting attention to questions about squares the author achieves the dual goals of making the presentation accessible to undergraduates and reflecting the historical roots of the subject. The representation of integers by quadratic forms is emphasized throughout the text. Lehman introduces an innovative notation for ideals of a quadratic domain that greatly facilitates computation and he uses this to particular effect. The text has an unusual focus on actual computation. This focus, and this notation, serve the author's historical purpose as well; ideals can be seen as number-like objects, as Kummer and Dedekind conceived of them. The notation can be adapted to quadratic forms and provides insight into the connection between quadratic forms and ideals. The computation of class groups and continued fraction representations are featured—the author's notation makes these computations particularly illuminating. Quadratic Number Theory, with its exceptionally clear prose, hundreds of exercises, and historical motivation, would make an excellent textbook for a second undergraduate course in number theory. The clarity of the exposition would also make it a terrific choice for independent reading. It will be exceptionally useful as a fruitful launching pad for undergraduate research projects in algebraic number theory.

Algorithms and Theory of Computation Handbook

Download Algorithms and Theory of Computation Handbook PDF Online Free

Author :
Publisher : CRC Press
ISBN 13 : 9781420049503
Total Pages : 1328 pages
Book Rating : 4.0/5 (495 download)

DOWNLOAD NOW!


Book Synopsis Algorithms and Theory of Computation Handbook by : Mikhail J. Atallah

Download or read book Algorithms and Theory of Computation Handbook written by Mikhail J. Atallah and published by CRC Press. This book was released on 1998-11-23 with total page 1328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Algorithms and Theory of Computation Handbook is a comprehensive collection of algorithms and data structures that also covers many theoretical issues. It offers a balanced perspective that reflects the needs of practitioners, including emphasis on applications within discussions on theoretical issues. Chapters include information on finite precision issues as well as discussion of specific algorithms where algorithmic techniques are of special importance, including graph drawing, robotics, forming a VLSI chip, vision and image processing, data compression, and cryptography. The book also presents some advanced topics in combinatorial optimization and parallel/distributed computing. • applications areas where algorithms and data structuring techniques are of special importance • graph drawing • robot algorithms • VLSI layout • vision and image processing algorithms • scheduling • electronic cash • data compression • dynamic graph algorithms • on-line algorithms • multidimensional data structures • cryptography • advanced topics in combinatorial optimization and parallel/distributed computing

The Mathematics of Ciphers

Download The Mathematics of Ciphers PDF Online Free

Author :
Publisher : CRC Press
ISBN 13 : 143986389X
Total Pages : 213 pages
Book Rating : 4.4/5 (398 download)

DOWNLOAD NOW!


Book Synopsis The Mathematics of Ciphers by : S.C. Coutinho

Download or read book The Mathematics of Ciphers written by S.C. Coutinho and published by CRC Press. This book was released on 1999-01-15 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is an introduction to the algorithmic aspects of number theory and its applications to cryptography, with special emphasis on the RSA cryptosys-tem. It covers many of the familiar topics of elementary number theory, all with an algorithmic twist. The text also includes many interesting historical notes.

The Whole Truth About Whole Numbers

Download The Whole Truth About Whole Numbers PDF Online Free

Author :
Publisher : Springer
ISBN 13 : 3319110357
Total Pages : 296 pages
Book Rating : 4.3/5 (191 download)

DOWNLOAD NOW!


Book Synopsis The Whole Truth About Whole Numbers by : Sylvia Forman

Download or read book The Whole Truth About Whole Numbers written by Sylvia Forman and published by Springer. This book was released on 2015-01-02 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Whole Truth About Whole Numbers is an introduction to the field of Number Theory for students in non-math and non-science majors who have studied at least two years of high school algebra. Rather than giving brief introductions to a wide variety of topics, this book provides an in-depth introduction to the field of Number Theory. The topics covered are many of those included in an introductory Number Theory course for mathematics majors, but the presentation is carefully tailored to meet the needs of elementary education, liberal arts, and other non-mathematical majors. The text covers logic and proofs, as well as major concepts in Number Theory, and contains an abundance of worked examples and exercises to both clearly illustrate concepts and evaluate the students’ mastery of the material.

Large Scale Linear and Integer Optimization: A Unified Approach

Download Large Scale Linear and Integer Optimization: A Unified Approach PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 1461549752
Total Pages : 739 pages
Book Rating : 4.4/5 (615 download)

DOWNLOAD NOW!


Book Synopsis Large Scale Linear and Integer Optimization: A Unified Approach by : Richard Kipp Martin

Download or read book Large Scale Linear and Integer Optimization: A Unified Approach written by Richard Kipp Martin and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 739 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a textbook about linear and integer linear optimization. There is a growing need in industries such as airline, trucking, and financial engineering to solve very large linear and integer linear optimization problems. Building these models requires uniquely trained individuals. Not only must they have a thorough understanding of the theory behind mathematical programming, they must have substantial knowledge of how to solve very large models in today's computing environment. The major goal of the book is to develop the theory of linear and integer linear optimization in a unified manner and then demonstrate how to use this theory in a modern computing environment to solve very large real world problems. After presenting introductory material in Part I, Part II of this book is de voted to the theory of linear and integer linear optimization. This theory is developed using two simple, but unifying ideas: projection and inverse projec tion. Through projection we take a system of linear inequalities and replace some of the variables with additional linear inequalities. Inverse projection, the dual of this process, involves replacing linear inequalities with additional variables. Fundamental results such as weak and strong duality, theorems of the alternative, complementary slackness, sensitivity analysis, finite basis the orems, etc. are all explained using projection or inverse projection. Indeed, a unique feature of this book is that these fundamental results are developed and explained before the simplex and interior point algorithms are presented.

Algebra 1

Download Algebra 1 PDF Online Free

Author :
Publisher : Springer
ISBN 13 : 9811042535
Total Pages : 439 pages
Book Rating : 4.8/5 (11 download)

DOWNLOAD NOW!


Book Synopsis Algebra 1 by : Ramji Lal

Download or read book Algebra 1 written by Ramji Lal and published by Springer. This book was released on 2017-05-07 with total page 439 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first in a series of three volumes dealing with important topics in algebra. It offers an introduction to the foundations of mathematics together with the fundamental algebraic structures, namely groups, rings, fields, and arithmetic. Intended as a text for undergraduate and graduate students of mathematics, it discusses all major topics in algebra with numerous motivating illustrations and exercises to enable readers to acquire a good understanding of the basic algebraic structures, which they can then use to find the exact or the most realistic solutions to their problems.

First Course in Algebra and Number Theory

Download First Course in Algebra and Number Theory PDF Online Free

Author :
Publisher : Elsevier
ISBN 13 : 1483270378
Total Pages : 560 pages
Book Rating : 4.4/5 (832 download)

DOWNLOAD NOW!


Book Synopsis First Course in Algebra and Number Theory by : Edwin Weiss

Download or read book First Course in Algebra and Number Theory written by Edwin Weiss and published by Elsevier. This book was released on 2014-05-10 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt: First Course in Algebra and Number Theory presents the basic concepts, tools, and techniques of modern algebra and number theory. It is designed for a full year course at the freshman or sophomore college level. The text is organized into four chapters. The first chapter is concerned with the set of all integers - positive, negative, and zero. It investigates properties of Z such as division algorithm, Euclidean algorithm, unique factorization, greatest common divisor, least common multiple, congruence, and radix representation. In chapter 2, additional axioms about Z were introduced and some of their consequences are discussed. The third chapter sets up terminologies about polynomials, solutions or roots of polynomial equations, and factorization of polynomials. Finally, chapter 4 studies logically simpler algebraic systems, known as "groups", algebraic objects with a single operation. The book is intended for students in the freshman and sophomore levels in college.

Integers, Fractions, and Arithmetic

Download Integers, Fractions, and Arithmetic PDF Online Free

Author :
Publisher : American Mathematical Soc.
ISBN 13 : 082188798X
Total Pages : 226 pages
Book Rating : 4.8/5 (218 download)

DOWNLOAD NOW!


Book Synopsis Integers, Fractions, and Arithmetic by : Judith D. Sally

Download or read book Integers, Fractions, and Arithmetic written by Judith D. Sally and published by American Mathematical Soc.. This book was released on 2012 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: A co-publication of the AMS and the Mathematical Sciences Research Institute. This book, which consists of twelve interactive seminars, is a comprehensive and careful study of the fundamental topics of K–8 arithmetic. The guide aims to help teachers understand the mathematical foundations of number theory in order to strengthen and enrich their mathematics classes. Five seminars are dedicated to fractions and decimals because of their importance in the classroom curriculum. The standard topics are covered in detail, but are arranged in an order that is slightly different from the usual one. Multiplication is treated first, and with that in hand, common denominators and equivalent fractions are more readily understood and are available for use when discussing addition. The book is intended for the professional development of teachers. It is appropriate for teacher education programs as well as for enrichment programs such as Mathematical Circles for Teachers. There are numerous activities in each seminar that teachers can bring into their classrooms. In the interest of fostering a greater awareness and appreciation of mathematics and its connections to other disciplines and everyday life, MSRI and the AMS are publishing books in the Mathematical Circles Library series as a service to young people, their parents and teachers, and the mathematics profession.--Publisher website.

Number Theory Through the Eyes of Sophie Germain

Download Number Theory Through the Eyes of Sophie Germain PDF Online Free

Author :
Publisher : American Mathematical Society
ISBN 13 : 1470472201
Total Pages : 216 pages
Book Rating : 4.4/5 (74 download)

DOWNLOAD NOW!


Book Synopsis Number Theory Through the Eyes of Sophie Germain by : David Pengelley

Download or read book Number Theory Through the Eyes of Sophie Germain written by David Pengelley and published by American Mathematical Society. This book was released on 2023-06-29 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Number Theory Through the Eyes of Sophie Germain: An Inquiry Course is an innovative textbook for an introductory number theory course. Sophie Germain (1776–1831) was largely self-taught in mathematics and, two centuries ago, in solitude, devised and implemented a plan to prove Fermat's Last Theorem. We have only recently completely understood this work from her unpublished letters and manuscripts. David Pengelley has been a driving force in unraveling this mystery and here he masterfully guides his readers along a path of discovery. Germain, because of her circumstances as the first woman to do important original mathematical research, was forced to learn most of what we now include in an undergraduate number theory course for herself. Pengelley has taken excerpts of her writings (and those of others) and, by asking his readers to decipher them, skillfully leads us through an inquiry-based course in elementary number theory. It is a detective story on multiple levels. What is Sophie Germain thinking? What do her mathematical writings mean? How do we understand what she knew and what she was trying to do, where she succeeded and where she didn't? Number Theory Through the Eyes of Sophie Germainis simultaneously a masterpiece of historical scholarship, a guide to reading and teaching from primary-source historical documents, an inquiry-based textbook for introductory number theory, and the riveting story of a major, but still unappreciated, mathematician. Work is required of the reader. Readers are carefully guided to discover and prove almost all results for themselves in a sequence of scaffolded exploratory tasks with hints, fully integrated with the narrative. The difficulty of the inquiry tasks varies considerably, but the author provides the reader with appropriately helpful guidance at every step. An introductory number theory course taught with this text would be a remarkable, potentially life-changing, experience. —Stephen Kennedy, Carleton College and MAA Press

Applied Algebra

Download Applied Algebra PDF Online Free

Author :
Publisher : CRC Press
ISBN 13 : 1420071432
Total Pages : 426 pages
Book Rating : 4.4/5 (2 download)

DOWNLOAD NOW!


Book Synopsis Applied Algebra by : Darel W. Hardy

Download or read book Applied Algebra written by Darel W. Hardy and published by CRC Press. This book was released on 2011-08-10 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using mathematical tools from number theory and finite fields, Applied Algebra: Codes, Ciphers, and Discrete Algorithms, Second Edition presents practical methods for solving problems in data security and data integrity. It is designed for an applied algebra course for students who have had prior classes in abstract or linear algebra. While the content has been reworked and improved, this edition continues to cover many algorithms that arise in cryptography and error-control codes. New to the Second Edition A CD-ROM containing an interactive version of the book that is powered by Scientific Notebook®, a mathematical word processor and easy-to-use computer algebra system New appendix that reviews prerequisite topics in algebra and number theory Double the number of exercises Instead of a general study on finite groups, the book considers finite groups of permutations and develops just enough of the theory of finite fields to facilitate construction of the fields used for error-control codes and the Advanced Encryption Standard. It also deals with integers and polynomials. Explaining the mathematics as needed, this text thoroughly explores how mathematical techniques can be used to solve practical problems. About the Authors Darel W. Hardy is Professor Emeritus in the Department of Mathematics at Colorado State University. His research interests include applied algebra and semigroups. Fred Richman is a professor in the Department of Mathematical Sciences at Florida Atlantic University. His research interests include Abelian group theory and constructive mathematics. Carol L. Walker is Associate Dean Emeritus in the Department of Mathematical Sciences at New Mexico State University. Her research interests include Abelian group theory, applications of homological algebra and category theory, and the mathematics of fuzzy sets and fuzzy logic.