Solve Using the Quadratic Formula x^2-18x-6=0

$x^{2} - 18 x - 6 = 0$

Step 1

Use the quadratic formula to find the solutions.

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

Step 2

Substitute the values $a = 1$ , $b = - 18$ , and $c = - 6$ into the quadratic formula and solve for $x$ .

$\frac{18 \pm \sqrt{{(- 18)}^{2} - 4 \cdot (1 \cdot - 6)}}{2 \cdot 1}$

Step 3

Simplify.

Simplify the numerator.

Raise $- 18$ to the power of $2$ .

$x = \frac{18 \pm \sqrt{324 - 4 \cdot 1 \cdot - 6}}{2 \cdot 1}$

Multiply $- 4 \cdot 1 \cdot - 6$ .

Multiply $- 4$ by $1$ .

$x = \frac{18 \pm \sqrt{324 - 4 \cdot - 6}}{2 \cdot 1}$

Multiply $- 4$ by $- 6$ .

$x = \frac{18 \pm \sqrt{324 + 24}}{2 \cdot 1}$

Add $324$ and $24$ .

$x = \frac{18 \pm \sqrt{348}}{2 \cdot 1}$

Rewrite $348$ as $2^{2} \cdot 87$ .

Factor $4$ out of $348$ .

$x = \frac{18 \pm \sqrt{4 (87)}}{2 \cdot 1}$

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

$x = \frac{18 \pm \sqrt{2^{2} \cdot 87}}{2 \cdot 1}$

Pull terms out from under the radical.

$x = \frac{18 \pm 2 \sqrt{87}}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{18 \pm 2 \sqrt{87}}{2}$

Simplify $\frac{18 \pm 2 \sqrt{87}}{2}$ .

$x = 9 \pm \sqrt{87}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$x = 9 \pm \sqrt{87}$

Decimal Form:

$x = 18.32737905 \dots, - 0.32737905 \dots$