x=(根号2+1)/2
根号2=2x-1
两边平方
(2x-1)^2=2
4x^2-4x+1=2
4x^2-4x=1
4x^4+4x^3-9x^2-2x+1
=4x^4-4x^3+8x^3-9x^2-2x+1=x^2(4x^2-4x)+8x^3-9x^2-2x+1
=x^2*1+8x^3-9x^2-2x+1
=8x^3-8x^2-2x+1
=2x(4x^2-4x)-2x+1
=2x*1-2x+1
=1