2x的平方+3=5x
2x²-5x=-3
x²-5x/2+25/16=-3/2+25/16
(x-5/4)²=1/16
x-5/4=1/4 x-5/4=-1/4
x=3/2 x=1
-3x的平方-2x+1=0
x²+2x/3+1/9=1/3+1/9
(x+1/3)²=4/9
x+1/3=2/3 x+1/3=-2/3
x=1/3 x=-1