Question

已知x的平方+x-1=0,求x的3次方+2x的平方+2006的值

Answer 1

x^2+x-1=0

=>x^2+x=1

x^3+2x^2+2006

=x(x^2+x)+x^2+2006

=x+x^2+2006

=1+2006

=2007