2x^2 -5x =6
=>x^2 - (5/2)x=3
=>x^2 - 2x*(5/4) +(5/4)^2 =3 +(25/16)
=>(x- 5/4 )^2 =73/16
=>x - 5/4 = ±√(73/16)
=> x=5/4 ±(√73 )/4 = (5±√73)/4