3x平方-5x=-2
x^2-5x/3=-2/3
(x-5/6)^2=1/36
x-5/6=土1/6
x1=1 x2=2/3
1/4x²-x-4=0
x^2-4x=16
(x-2)^2=20
x-2=±2√5
x1=2+2√5 x2=2-2√5 .