Find all real solutions of the equation by completing the square. x2 + 6x − 12 = 0

To complete the square we:

Move the non-x tern to the right  x^2 + 6c = 12

Divide the equation by the coefficient of x^2 (already done)

Next we take the coefficient of x, divide it by 2, square it, then add it to both sides.

6 / 2 = 3 then 3^2 = 9 then adding to both sides

x^2 + 6x + 9 = 12 +9

(x+3)^2 = 21 then taking the square root of both sides:

x + 3 = square root (21)

x = square root (21) -3  equals 4.582575695 -3

x1 = 1.582575695

AND remebering the square root (21) also = -4.582575695 then

x2 = -7.582575695

Source: 1728.com/quadr2.htm