已知x2+x-1=0,求x³+2x²+2006
问题描述：
已知x2+x-1=0,求x³+2x²+2006
答
答：
x^2+x-1=0
x^2=1-x
x^3+2x^2+2006
=(1-x)x+2x^2+2006
=x+x^2+2006
=1+2006
=2007