Question

(x+y) 2+ (x−y) 2 e ao quadrado esses numeros 2

Answer 1

(x+y)²+(x-y)² = 
(x+y)*(x+y) + (x-y)*(x-y) =
x²+xy+yx+y² + x²-xy-yx+y²= 
x²+x²+xy-xy+yx-yx+y²+y²=
2x²+2y²