Question

(5x-2y)2 - 4(5x+2y) (5x-2y)

Answer 1

$(5x -2y)^{2} - 4*(5x+2y)(5x-2y)$
$25x^{2}-2*5x*2y+4y^{2}- 4*((5x)^{2}-(2y)^{2})$
$25x^{2}-20*xy+4y^{2}- 4*(25x^{2}-4y^{2})$
$25x^{2}-20*xy+4y^{2}- 100x^{2}+16y^{2}$
$-75x^{2}-20*xy+20y^{2}$
$(-25x+10y)(3x+2y)$