解(x+2y)(-x-2y)=(x+2y)[-(x+2y)]=-(x+2y)²=-(x²+4xy+4y²)=-x²-4xy-4y²(2x-3y)²-(4y-3x)(3x+4y)=(4x²-12xy+9y²)-(16y²-9x²)=(4x²+9x²)-12xy+(9y²...