x²+x=1
所以x²=1-x
x的立方+2x平方+2006
=（x³+2x²）+2006
=x²（x+2）+2006
=（1-x）（2+x）+2006
=2-x-x²+2006
=2-（x+x²）+2006
=2-1+2006
=2007