x^2-x+1>0
所以 3x = x^2 - x + 1
x^2 - 4x +1 = 0
x = 2+根号3 或 2-根号3
x^2 + x + 1 = 5x
所以 原式 = x/5
= (2+根号3)/5 或 (2-根号3)/5