(x的平方-2y的平方)(x+2y)-2xy(x-y)其中x=-2,y=-1/2=(x-2y)(x+2y)(x+2y)-2x²y+2xy²=[-2-2*(-1/2)][-2+2*(-1/2)]²-2*(-2)²*(-1/2)+2*(-2)*(-1/2)²=(-2+1)(-2-1)²+4-1=-9+3=-6