Question

先化简,再求值：2(x-2y)的平方-4(x+3y)(x-3y)+2(x-y)(2y+x),其中x=-4,y=-3.

Answer 1

2(x-2y)²-4(x+3y)(x--3y)+2(x-y)(2y+x)

=2(x²-4xy+y²)-4(x²-9y²)+(2x-2y)(2y+x)

=2x²-8xy+2y²-4x²+9y²+(x+x-2y)(x+2y)

=2x²-8xy+2y²-4x²+9y²+x²+2xy+x²-4y²

=-6xy+7y²

=-6*(-4)(-3)+7(-3)²

=-9