3x^2-5x+1=0
x^2-(5/3)x+1/3=0
(x-5/6)^2+1/3-25/36=0
(x-5/6)^2=13/36
x-5/6=√13/6
x=5/6+√13/6
或 x-5/6=-√13/6
x=5/6-√13/6