100х^2-4 (7х-2у)^2?=?

Question

100х^2-4 (7х-2у)^2?=?

Answer 1

100x^2-4(7x-2y)^2
100x^2-4(49x^2-28xy+4y^2)
100x^2-196x^2+112xy-16y^2
96x^2-112xy+16y^2
6x^2-7xy+y^2
6x^2-6xy-xy+y^2
6x(x-y)-y(x-y)
(6x-y)(x-y)