(b) For all integers n, if n is a multiple of 3, then n can be written as the sum of consecutive
(c) For all integers a and b, if a^2 + b^2 is odd, then a or b is odd.
Proof by contrapositive. This proof starts by letting a and b be integers. Then
assume that a and b are even. This proof ends with a^2 + b^2 even.
Consider the statement: for all integers n, if n is even then 8n is even.
(a) Prove the statement. What sort of proof are you using?