题目应该是x+y=1,应该是印刷掉了
x^3+Y^3+3xy
= (ax+y) (x^2-xy+y^2)+3xy
=(x^2-xy+y^2)+3xy
=x^2-xy+y^2+3xy
=x^2+2xy+y^2
=(x+y)²
=1