Question

Докажите тождество 2(х+у)(x-y)+(x+y)^2+(x-y)^2=4x^2

Answer 1

$2(x+y)(x-y)+(x+y)^2+(x-y)^2= \ =2x^2-2y^2+x^2+2xy+y^2+x^2-2xy+y^2 \ =2x^2+2x^2= \ =4x^2$