Prove:
for all integers n, if n2 is odd, then n is odd.
use a proof by contraposition, as in lemma 1.1.
let n be an integer. suppose that n is even, i. e., n = for some integer k. then n2 = = 2
is also even.

Given the statement, "If is odd, then is odd," its contrapositive claims that, "If is not odd, then is not odd."

So assume is not odd, i.e. is even. This means there is an integer for which . Squaring this gives .

Well, we can write , and is just another integer, which means must be even.

Maybe fx = lxl because of the way the x is positioned is that what he