tentukan himpunan penyelesaian persamaan kuadrat berikut dengan menlengkapkan bentuk kuadrat sempurna! 2x^2 -x -1 =0

2x^2 -x -1 = 0
2x^2 - x = 1..(dibagi 2)
x^2 -1/2x = 1/2
(x - 1/4)^2 -(1/4)^2 = 1/2
(x -1/4)^2 = 1/2+ (1/4)^2
(x - 1/4x)^2 = 1/2 + 1/16
(x - 1/4)^2 = 17/16
(x - 1/4) = +/-√(17/16)
(x -1/4) = +/- (√17)/4
x1 = (√17+1/4)
x1 = {√17+1)/4
x2 = -(√17)/4 +1/4
x2 = (-√17+1)/4