x加y的三次方等于什么?

问题描述:

x加y的三次方等于什么?

(x+y)³=x³+3x²y+3xy²+y³
(x+y)³=(x+y)²(x+y)
=(x²+2xy+y²)(x+y)
=x³+x²y+2x²y+2xy²+xy²+y³
=x³+3x²y+3xy²+y³