Question

ребята помогите срочно надо))))

Answer 1

$(-7x+9y)^2-14x(4x-9y)+7x^2= \ \ =49x^2-126xy+81y^2-56x^2+126xy+7x^2=81y^2 \ \ y= sqrt{2} \ \ 81*( sqrt{2})^2=81*2=162$