已知x+y=3,xy=-2,求x^3+y^3的值fast!
问题描述:
已知x+y=3,xy=-2,求x^3+y^3的值
fast!
答
x^3+y^3
=(x+y)(x²-xy+y²)
=(x+y)[(x+y)²-3xy]
=3×(3²+6)
=45