Solve by Completing the Square x^2+4x-4=0

$x^{2} + 4 x - 4 = 0$

Step 1

Add $4$ to both sides of the equation.

$x^{2} + 4 x = 4$

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 $b$ .

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

Step 3

Add the term to each side of the equation.

$x^{2} + 4 x + {(2)}^{2} = 4 + {(2)}^{2}$

Step 4

Simplify the equation.

Simplify the left side.

Raise $2$ to the power of $2$ .

$x^{2} + 4 x + 4 = 4 + {(2)}^{2}$

Simplify the right side.

Simplify $4 + {(2)}^{2}$ .

Raise $2$ to the power of $2$ .

$x^{2} + 4 x + 4 = 4 + 4$

Add $4$ and $4$ .

$x^{2} + 4 x + 4 = 8$

Step 5

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

${(x + 2)}^{2} = 8$

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.

$x + 2 = \pm \sqrt{8}$

Simplify $\pm \sqrt{8}$ .

Rewrite $8$ as $2^{2} \cdot 2$ .

Factor $4$ out of $8$ .

$x + 2 = \pm \sqrt{4 (2)}$

Rewrite $4$ as $2^{2}$ .

$x + 2 = \pm \sqrt{2^{2} \cdot 2}$

Pull terms out from under the radical.

$x + 2 = \pm 2 \sqrt{2}$

Subtract $2$ from both sides of the equation.

$x = \pm 2 \sqrt{2} - 2$

Step 7

The result can be shown in multiple forms.

Exact Form:

$x = \pm 2 \sqrt{2} - 2$

Decimal Form:

$x = 0.82842712 \dots, - 4.82842712 \dots$