x4－2y4－2x3y＋xy3

分类: 作业答案 • 2023-01-12 14:12:06

问题描述：

x4－2y4－2x3y＋xy3
为什么不能这样算?
原式=x3(x-2y)-y3(2y-x)
=x3(x-2y)+y3(x-2y)
=(x-2y)(x3+y3)
另外：x3-y3的公式是?

答

原式=x3(x-2y)-y3(2y-x)
=x3(x-2y)+y3(x-2y)
=(x-2y)(x3+y3)
=(x-2y)(x+y)(x2-xy+y2)
x3-y3=(x-y)(x2+xy+y2)
x3+y3=(x+y)(x2-xy+y2)