Question

Доказать тождество:
(a+b)^2-(a-b)^2=4b

Answer 1

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