а-16=(√а)²-4²=(√а-4)(√а+4)
(√а-4)(√√а+4)/(√а+4)=√а-4
(5x^2 - 10xy + 5y^2) / (2x^2 - 2xy + 2y^2) : (8x - 8y) / (10x^3 + 10y^3) =
5(x^2 - 2xy + y^2) / 2(x^2 - xy + y^2) : 8(x -y) / 10(x^3 + y^3) =
5((x - y)(x - y)) / 2(x^2 - xy + y^2) : 8(x - y) / 10((x + y)(x^2 - xy + y^2))=
25((x - y)(x + y)) / 8 = (25(x^2 - y^2)) / 8
3√72 - 8√2 = 3√(36*2) - 8√2 = 3*6√2 - 8√2 = 18√2 - 8√2 =10√2