2x²-x-1=0
2(x²-x/2)-1=0
2(x²-x/2+1/16)-1-1/8=0
2(x-1/4)²=9/8
(x-1/4)²=9/16
(x-1/4)=±3/4
x=1/4±3/4
∴x1=1 x2=-1/2