Chapter 1: Problem 1
Use a direct proof to show that the sum of two odd integers is even.
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These are the key concepts you need to understand to accurately answer the question.
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Chapter 1: Problem 1
Use a direct proof to show that the sum of two odd integers is even.
These are the key concepts you need to understand to accurately answer the question.
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Express the negation of these propositions using quantifiers, and then express the negation in English. a) Some drivers do not obey the speed limit. b) All Swedish movies are serious. c) No one can keep a secret. d) There is someone in this class who does not have a good attitude.
Use a proof by exhaustion to show that a tiling using dominoes of a \(4 \times 4\) checkerboard with opposite corners removed does not exist. [Hint: First show that you can assume that the squares in the upper left and lower right corners are removed. Number the squares of the original checkerboard from 1 to \(16,\) starting in the first row, moving right in this row, then starting in the leftmost square in the second row and moving right, and so on. Remove squares 1 and \(16 .\) To begin the proof, note that square 2 is covered either by a domino laid horizontally, which covers squares 2 and \(3,\) or vertically, which covers squares 2 and \(6 .\) Consider each of these cases separately, and work through all the subcases that arise. \(]\)
Prove that given a real number \(x\) there exist unique numbers \(n\) and \(\epsilon\) such that \(x=n+\epsilon, n\) is an integer, and \(0 \leq \epsilon<1 .\)
Determine the truth value of each of these statements if the domain for all variables consists of all integers. $$ \begin{array}{ll}{\text { a) } \forall n\left(n^{2} \geq 0\right)} & {\text { b) } \exists n\left(n^{2}=2\right)} \\ {\text { c) } \forall n\left(n^{2} \geq n\right)} & {\text { d) } \exists n\left(n^{2}<0\right)}\end{array} $$
Exercises \(48-51\) establish rules for null quantification that we can use when a quantified variable does not appear in part of a statement. Establish these logical equivalences, where \(x\) does not occur as a free variable in \(A\) . Assume that the domain is nonempty. $$ \begin{array}{l}{\text { a) } \forall x(A \rightarrow P(x)) \equiv A \rightarrow \forall x P(x)} \\ {\text { b) } \exists x(A \rightarrow P(x)) \equiv A \rightarrow \exists x P(x)}\end{array} $$
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