问题描述： x³+y³+z³-3xyz为什么等于(x+y+z)(x²+y²+z²-xy-yz-xz) 1个回答 分类：数学 2014-10-22 问题解答： 我来补答 x³+y³+z³-3xyz=(x+y)³-3x²y-3xy²+z³-3xyz=(x+y)³+z³-(3x²y+3xy²+3xyz)=(x+y+z)[(x+y)²-(x+y)z+z²]-3xy(x+y+z)=(x+y+z)[(x+y)²-(x+y)z+z²-3xy]=(x+y+z)(x²+2xy+y²-xz-yz+z²-3xy)=(x+y+z)(x²+y²+z²-xy-xz-yz) 展开全文阅读
