2x²-9x=-1
x²-9x/2=-1/2
x²-9x/2+81/16=73/16
(x-9/4)²=73/16
∴x=9/4+√73/4 x=9/4-√73/4
3x²+2x-1=0
(3x-1)(x+1)=0
∴x=1/3 x=-1