若x²+x-1=0,求x³+2x²-7的值(求详细的过程,谢谢了)

2024-12-14 03:44:19
推荐回答(1个)
回答1:

x²=-x+1
x³=x(x²)
=x(-x+1)
=-x²+x

所以原式=-x²+x+2x²-7
=x²+x-7
=x²+x-1-6
=0-6
=-6