2x^2-5x+6=0可化为
x^2-(5/2)x+3=0
x^2-2(5/4)x+(5/4)^2+3-(5/4)^2=0
(x-5/4)^2+(48-25)/16=0
(x-5/4)^2+23/16=0
所以,原方程无解.