Looking at the "
Square of an Odd" puzzle that asks to prove that the square of an odd number is always 1 more than a multiple of 8, a professor gave this four parts proof: "All odd numbers are of the form 8K+1, 8K+3, 8K+5 or 8K+7. Squaring these numbers produces 8M+1, 8M+9, 8M+25 or 8M+49, which are all of the form 8N+1. QED"
Another professor came by, and gave a single line proof. Can you manage it?
Note: no one who answered the original problem produced either the four parts solution, or the single line one.
(In reply to
my way by Ady TZIDON)
11 years on:
Because (2n+1)^2(2n1)^2 = 8n, all odd numbers must be worth the same as 1, mod 8, namely 1.
Edited on June 24, 2016, 11:50 pm

Posted by broll
on 20160624 23:39:48 