# product of odd numbers is odd question

i know how to prove that the product of two odd numbers is odd, but how would i go about proving the other direction... What if i needed to use this as an if and only if statement in a proof, thanks

• Hint: Try proving the contrapositive. That is to say, if at least one of $a,b$ is even prove that $a\times b$ must also be even. Do you see why this is equivalent to showing that if $a\times b$ is odd then $a$ and $b$ are both odd? – JMoravitz Nov 8 '18 at 1:12
• ok thanks i will try – Carlos Bacca Nov 8 '18 at 1:13