x={(根号5)-1}/2是方程x^2+x-1=0的根,
2x^5-3x^4+4x^3+x^2+1
=2x^3(x^2+x-1)-5x^4+6x^3+x^2+1
=-5x^4+6x^3+x^2+1
=-5x^2(x^2+x-1)+11x^3-4x^2+1
=11x^3-4x^2+1
=11x(x^2+x-1)-15x^2+11x+1
=-15x^2+11x+1
=-15(x^2+x-1)+26x-14
=26x-14
=13(根号5)-27