已知x²+x-1=0则x³+2x²-3=

问题描述:

已知x²+x-1=0则x³+2x²-3=

x²+x-1=0
x²+x=1

x³+2x²-3
=x³+x²+x²-3
=x(x²+x)+x²-3
=x+x²-3
=1-3
=-2