x+y=1xy=-1 求x3+y3=?
问题描述：
x+y=1xy=-1 求x3+y3=?
如题,我急需啊~~~希望快点,在线等
答
x+y=1,
(x+y)^2=1,x^2+2xy+y^2=1,
x^2+y^2=3
x^3+y^3
=(x+y)(x^2-xy+y^2)
=4