2x^2+1=3x
x^2-3x/2=-1/2
x^2-2*x*3/4+(3/4)^2=-1/2+(3/4)^2
(x-3/4)^2=1/16
x-3/4=(+ -) 1/4
x=1
x=1/2
…………
x^2-6x+1=0
x^2-2*x*3+9=8
(x-3)^2=8
x-3=（+ -）2根号2
x=3+2根号2
x=3-2根号2