Question

I'm trying to find the value that completes the square

Answer 1

1) Move the non-x term to the right
x^2 +6x = -c

2) Divide the equation by the coefficient of x^2
(You don't have to because it is one).

3) Get the "x" coefficient, divide it by 2, square it then add it to both sides:
6 divided by 2 = 3
3^2 = 9

x^2 +6x +9 = -c +9
Take the square root of both sides
(x +3) = sq root (9 -c)
x = -3 + sq root (9 -c)