若x的三次方+y的三次方=27,x²-xy+y²=9,则x+y=...
问题描述:
若x的三次方+y的三次方=27,x²-xy+y²=9,则x+y=...
答
x^3+y^3
=(x+y)(x^2-xy+y^2)
x+y=27÷9=3