2x^2－5x＋2＝0
x^2－5/2x＋1＝0
x^2－5/2x＋(5/4)^2 -(5/4)^2 +1＝0
(x-5/4)^2 =9/16
x-5/4 =3/4或x-5/2 =-3/4
x=2或x =1/2