Discrete Mathematics with Applications 4th Edition

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

Chapter 8 - Relations - Exercise Set 8.2 - Page 458: 19

Answer

Not Reflexive Symmetric Not Transative

Work Step by Step

Define a relation I on R as follows: For all real numbers x and y, x I y ⇔ x − y is irrational. Reflexive: for all x ∈ Z xAx false since x-x = 0 (note that 0 is rational = 0/1) Symmetric: for all x,y ∈ Z if xIy then yIx xIy <=> x-y = irrational number X -x+y = -X (muliplie by -1) y - x = -X (commutive law, adding -Sign wont change the fact that X is irrational) hence yIx by definition of I Transitive: for all x,y, and z ∈ Z if (xIy and yIz) then xIz let x = $\sqrt{2}$, y = 1, z = $\sqrt{2}$ xIy <=> x-y = $\sqrt{2}$ - 1 , irrational yIz <=> y-z = 1 - $\sqrt{2}$ , irrational but xIz <=> $\sqrt{2}$ - $\sqrt{2}$ = rational{hence false}
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.