2x^2-5x=-2
2(x^2-5x/2+25/16)=25/8-2
2(x-5/4)^2=25/8-16/8
2(x-5/4)^2=9/8
(x-5/4)^2=9/16
所以：
x-5/4=±3/4
即x=1/2或者x=2.