$-5x+2y$2 = $-5x+2y$$-5x+2y$ = $-5x$$-5x$ + $-5x$$2y$ + $2y$$-5x$ + $2y$$2y$ = 25x^2 - 10xy - 10xy + 4y^2
= 25x^2 - 20xy + 4y^2