Solve Using the Quadratic Formula 2x^2-8x-4=0

$2 x^{2} - 8 x - 4 = 0$

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 $a = 2$ , $b = - 8$ , and $c = - 4$ into the quadratic formula and solve for $x$ .

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

Step 3

Simplify.

Simplify the numerator.

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

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

Multiply $- 4 \cdot 2 \cdot - 4$ .

Multiply $- 4$ by $2$ .

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

Multiply $- 8$ by $- 4$ .

$x = \frac{8 \pm \sqrt{64 + 32}}{2 \cdot 2}$

Add $64$ and $32$ .

$x = \frac{8 \pm \sqrt{96}}{2 \cdot 2}$

Rewrite $96$ as $4^{2} \cdot 6$ .

Factor $16$ out of $96$ .

$x = \frac{8 \pm \sqrt{16 (6)}}{2 \cdot 2}$

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

$x = \frac{8 \pm \sqrt{4^{2} \cdot 6}}{2 \cdot 2}$

Pull terms out from under the radical.

$x = \frac{8 \pm 4 \sqrt{6}}{2 \cdot 2}$

Multiply $2$ by $2$ .

$x = \frac{8 \pm 4 \sqrt{6}}{4}$

Simplify $\frac{8 \pm 4 \sqrt{6}}{4}$ .

$x = 2 \pm \sqrt{6}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$x = 2 \pm \sqrt{6}$

Decimal Form:

$x = 4.44948974 \dots, - 0.44948974 \dots$