Solve by Completing the Square x^2+2x-12=0

$x^{2} + 2 x - 12 = 0$

Step 1

Add $12$ to both sides of the equation.

$x^{2} + 2 x = 12$

Step 2

To create a trinomial square on the left side of the equation, find a value that is equal to the square of half of $b$ .

${(\frac{b}{2})}^{2} = {(1)}^{2}$

Step 3

Add the term to each side of the equation.

$x^{2} + 2 x + {(1)}^{2} = 12 + {(1)}^{2}$

Step 4

Simplify the equation.

Simplify the left side.

One to any power is one.

$x^{2} + 2 x + 1 = 12 + {(1)}^{2}$

Simplify the right side.

Simplify $12 + {(1)}^{2}$ .

One to any power is one.

$x^{2} + 2 x + 1 = 12 + 1$

Add $12$ and $1$ .

$x^{2} + 2 x + 1 = 13$

Step 5

Factor the perfect trinomial square into ${(x + 1)}^{2}$ .

${(x + 1)}^{2} = 13$

Step 6

Solve the equation for $x$ .

Take the specified root of both sides of the equation to eliminate the exponent on the left side.

$x + 1 = \pm \sqrt{13}$

Subtract $1$ from both sides of the equation.

$x = \pm \sqrt{13} - 1$

Step 7

The result can be shown in multiple forms.

Exact Form:

$x = \pm \sqrt{13} - 1$

Decimal Form:

$x = 2.60555127 \dots, - 4.60555127 \dots$