已知x=根号5减去1的差除以2 ,则x^6 +2x^3-x^2 +1=

x=(根号5－1）／2
2x=根号5－1
2X＋1＝根号5
平方得：
4x^2+4x+1=5
x^2+x-1=0
x^2=1-x
x^6 +2x^3-x^2 +1
=(1-x)^3+2x*(1-x)-(1-x)+1
=(1-x^3-3x+3x^2)+2x-2x^2-1+x+1
=-x^3+x^2+1
=-x(1-x)+x^2+1
=-x+x^2+x^2+1
=-x+2(1-x)+1
=-3x+3
=-(根号5－1）/2*3＋3
＝ -3/2*根号5 +9/2