![Example 14 - Chapter 14 Class 11 Mathematical Reasoning - Part 2](https://d1avenlh0i1xmr.cloudfront.net/8adf43a9-628f-4a7d-bcc6-c2d3e760e593/slide49.jpg)
![Example 14 - Chapter 14 Class 11 Mathematical Reasoning - Part 3](https://d1avenlh0i1xmr.cloudfront.net/048c7563-2e2b-4b3c-ba14-2a06cebb520b/slide50.jpg)
Proving True - By Contrapositive
Last updated at April 16, 2024 by Teachoo
Example 14 Check whether the following statement is true or false by proving its contrapositive. If x, y ∈ Ζ such that xy is odd, then both x and y are odd. Let p : xy is odd. q : both x and y are odd. The given statement is of the form it p then q i.e. p ⇒ q We have to check the validity of statement by contrapositive method. i.e. x and y are not odd & prove that is false i.e. prove that xy is not odd Now consider x & y are not odd i.e. x & y are even let x = 2n for same n, m ∈ Z & t = 2m Calculate xy = 2n × 2m if n, m ∈ Z = 4mn ⇒ nm ∈ Z = 2 (2 m n) ⇒ 2n m ∈ Z This show xy is even ⇒ xy is not odd ⇒ p is false ⇒ ~ p Hence ~ q ⇒ ~ p