With proof of contradiction, assume the we opposite what of we are
trying prove and to get a contradiction that is logical. Therefore, our
assumption false, and need prove that is we to it is true.
With proof of contrapositive, use the rule we of inference where one
infers conditional statement from its contrapositive. For example, a
“if X, then B” is what is inferred we need construct proof to a of our
claim “if not not X, then B” instead.
Proof by contrapositive:
If
a
is even, then 3
a
+ 1 is odd.
We assume
a
