solve 20x^2 - 4x - 1=0
Multiply everything by 80 (80 = 4 * 20 - coefft of x^2)
1600x^2 - 320x - 80 = 0
rewrite this as
[(40x - 4)^2 - 16] - 80 = 0
(40x - 4)^2 = 96
(40x - 4) = +/- 4.rt(6)
40x = 4 +/- 4.rt(6)
x = (4 - 4.rt(6))/40, x = (4 + 4.rt(6))/40
x = (1 - rt(6))/10, x = (1 + rt(6))/10