Question

докажите справедливость равенства: (x-y)^2 + (x+y)^2 = 2(x^2 + y^2)

Answer 1

x^2-2xy+y^2+x^2+2xy+y^2=2x^2+2y^2
2x^2+2y^2=2x^2+2y^2