题目应该为：(x²+2x）²-（2x+4）²=[(x²+2x）+（2x+4)][(x²+2x-(2x+4)]=(x²+2x+2x+4)(x²+2x-2x-4)=(x²+4x+4)(x²-4)=(x+2)²(x+2)(x-2)