Question

Докажите тождество:

(а+b)2-4ab=(a-b)2

Answer 1

$a^{2} +2ab+ b^{2} -4ab= a^{2} -2ab+ b^{2} \ (a^{2} +2ab+ b^{2} -4ab)- (a^{2} -2ab+ b^{2})=0 \ a^{2} +2ab+ b^{2} -4ab-a^{2}+2ab-b^{2}=0$ , ч.т.д.