Discrete Mathematics and Its Applications, Seventh Edition

Published by McGraw-Hill Education
ISBN 10: 0073383090
ISBN 13: 978-0-07338-309-5

Chapter 1 - Section 1.4 - Predicates and Quantifiers - Exercises - Page 56: 43

Answer

$\forall x(P(x)\rightarrow Q(x))$ and $\forall xP(x)\rightarrow \forall xQ(x)$ are not logically equivalent.

Work Step by Step

Assume that the domain contain y and z for which P(y) is false, Q(y) is false, P(z) is true and Q(z) is false. Then, $\forall x(P(x)\rightarrow Q(x))$ is false (since for x=z, P(z) is true but Q(z) is false) but $\forall xP(x)\rightarrow \forall xQ(x)$ is true (since $\forall x P(x) $ is false). Hence, $\forall x(P(x)\rightarrow Q(x))$ and $\forall xP(x)\rightarrow \forall xQ(x)$ are not logically equivalent.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.