Solve for x x(x+8)=-20

$x (x + 8) = - 20$

Simplify $x (x + 8)$ .

Apply the distributive property.

$x \cdot x + x \cdot 8 = - 20$

Simplify the expression.

Multiply $x$ by $x$ .

$x^{2} + x \cdot 8 = - 20$

Move $8$ to the left of $x$ .

$x^{2} + 8 x = - 20$

Add $20$ to both sides of the equation.

$x^{2} + 8 x + 20 = 0$

Use the quadratic formula to find the solutions.

$\frac{- b \pm \sqrt{b^{2} - 4 (a c)}}{2 a}$

Substitute the values $a = 1$ , $b = 8$ , and $c = 20$ into the quadratic formula and solve for $x$ .

$\frac{- 8 \pm \sqrt{8^{2} - 4 \cdot (1 \cdot 20)}}{2 \cdot 1}$

Simplify.

Simplify the numerator.

Raise $8$ to the power of $2$ .

$x = \frac{- 8 \pm \sqrt{64 - 4 \cdot 1 \cdot 20}}{2 \cdot 1}$

Multiply $- 4$ by $1$ .

$x = \frac{- 8 \pm \sqrt{64 - 4 \cdot 20}}{2 \cdot 1}$

Multiply $- 4$ by $20$ .

$x = \frac{- 8 \pm \sqrt{64 - 80}}{2 \cdot 1}$

Subtract $80$ from $64$ .

$x = \frac{- 8 \pm \sqrt{- 16}}{2 \cdot 1}$

Rewrite $- 16$ as $- 1 (16)$ .

$x = \frac{- 8 \pm \sqrt{- 1 \cdot 16}}{2 \cdot 1}$

Rewrite $\sqrt{- 1 (16)}$ as $\sqrt{- 1} \cdot \sqrt{16}$ .

$x = \frac{- 8 \pm \sqrt{- 1} \cdot \sqrt{16}}{2 \cdot 1}$

Rewrite $\sqrt{- 1}$ as $i$ .

$x = \frac{- 8 \pm i \cdot \sqrt{16}}{2 \cdot 1}$

Rewrite $16$ as $4^{2}$ .

$x = \frac{- 8 \pm i \cdot \sqrt{4^{2}}}{2 \cdot 1}$

Pull terms out from under the radical, assuming positive real numbers.

$x = \frac{- 8 \pm i \cdot 4}{2 \cdot 1}$

Move $4$ to the left of $i$ .

$x = \frac{- 8 \pm 4 i}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{- 8 \pm 4 i}{2}$

Simplify $\frac{- 8 \pm 4 i}{2}$ .

$x = - 4 \pm 2 i$

The final answer is the combination of both solutions.

$x = - 4 + 2 i, - 4 - 2 i$