Discrete Mathematics with Applications 4th Edition

Published by Cengage Learning
ISBN 10: 0-49539-132-8
ISBN 13: 978-0-49539-132-6

Chapter 3 - The Logic of Quantified Statements - Exercise Set 3.2 - Page 117: 28

Answer

Statement: $\forall x \in \mathbb{R}$, if x(x + 1) > 0 then x > 0 or x < −1. Contrapositive: $\forall x \in \mathbb{R}$, if x ≤ 0 and x ≥ −1, then x(x + 1) ≤ 0. Converse: $\forall x \in \mathbb{R}$, if x > 0 or x < −1 then x(x + 1) > 0. Inverse: $\forall x \in \mathbb{R}$, if x(x + 1) ≤ 0 then x ≤ 0 and x ≥ −1. The statement, its contrapositive, its converse, and its inverse are all true.

Work Step by Step

A statement of the form: $\forall x \in D$, if P(x) then Q(x), has as its contrapositive statement: $\forall x \in D$, if ~Q(x) then ~P(x), as its converse statement: $\forall x \in D$, if Q(x) then P(x), and as its inverse statement: $\forall x \in D$, if ~P(x) then ~Q(x).
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