Completing the square 5x^2-20x+12?

5x^2 - 20x + 12 = 0
5 (x^2 - 4x) + 12 = 0
5 (x^2 - 4x + 4) + 8 = 0
then convert in form of a(x+b)^2 = c,
is 5 (x - 2)^2 = -8
thus,
a = 5, b = -2, and the value of c is equal to -8

5x² - 20x + 12 = 0
x² - 4x = - 12/5
x² - 2x = - 12/5 + (- 2)²
x² - 2x = - 12/5 + 4
x² - 2x = - 12/5 + 20/5
(x - 2)² = 8/5
x - 2 = +/- 1.2649111

x = 1.2649111 + 2, x = 3.2649111
x = - 1.2649111 + 2, x = 0.7350889

Answer: x = 3.2649111, 0.7350889

x= 10+/-2sqrt2/ 5

5x^2 - 20x + 12

= 5(x^2 - 4x) + 12

= 5(x^2 - 4x + 2^2 - 2^2) + 12

= 5[(x - 2)^2 - 4] + 12

= 5(x - 2)^2 - 20 + 12

= 5(x - 2)^2 - 8

completing the square according to my calculations

1(x - 2)² - 8/5 = 0

roots:

x = 2 ± √8/5

5x^2-20x=-12
5(x^2-4x)=-12
5[(x-2)^2-4]=-12
5(x-2)^2-20=-12
5(x-2)^2-8=0

5 ( x ² - 4 x ) + 12

5 ( x ² - 4x + 4) + 12 - 20

5 ( x - 2 ) ² - 8

c = - 8

5x^2 - 20x + 12
= 5(x^2 - 4x + 12/5)
= 5(x^2 - 2x - 2x + 12/5)
= 5(x^2 - 2x - 2x + 4 + 12/5 - 4)
= 5[(x^2 - 2x) - (2x - 4) + 12/5 - 20/5]
= 5[x(x - 2) - 2(x - 2) - 8/5]
= 5[(x - 2)^2 - 8/5]
= 5(x - 2)^2 - 8

a = 5
b = -2
c = -8