Question

докажите тождество (а+б)^2+(а-б)^2=2(а^2+б^2)

Answer 1

2а+2b+2a+2b=4a+4b
4a+4b=4a+4b

Answer 2

$(a+b)^2 + (a-b)^2 = 2(a^2+b^2) \\ a^2+2ab+b^2 + a^2 - 2ab + b^2 = 2(a^2 + b^2) \\ 2a^2 + 2b^2 = 2(a^2+b^2) \\ 2(a^2+b^2) = 2(a^2+b^2)$