solve 20x^2 - 4x - 1=0

Question

Solve using completing the square method

Answer 1

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