已知x2-x-1=0,则-x3+2x2+2004的值为_____.
问题描述：
已知x2-x-1=0,则-x3+2x2+2004的值为_____.
答
-x3+2x2+2004
=-x^3+x^2+x+x^2-x-1+2005
=-x(x^2-x-1)+(x^2-x-1)+2005
=2005