(-5a-2b)(5a+2B)
问题描述：
(-5a-2b)(5a+2B)
答
=-(5a+2b)²
=-(25a²+20ab+4b²)
=-25a²-20ab-4b²怎么做(x+1\2)^2(x-1\2)^2=[(x+1/2)(x-1/2)]²=(x² -1/4)²=x的4次方-x²/2+1/16