Solve Using the Quadratic Formula 4x^2+8x-5=0

$4 x^{2} + 8 x - 5 = 0$

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 $a = 4$ , $b = 8$ , and $c = - 5$ into the quadratic formula and solve for $x$ .

$\frac{- 8 \pm \sqrt{8^{2} - 4 \cdot (4 \cdot - 5)}}{2 \cdot 4}$

Step 3

Simplify.

Simplify the numerator.

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

$x = \frac{- 8 \pm \sqrt{64 - 4 \cdot 4 \cdot - 5}}{2 \cdot 4}$

Multiply $- 4 \cdot 4 \cdot - 5$ .

Multiply $- 4$ by $4$ .

$x = \frac{- 8 \pm \sqrt{64 - 16 \cdot - 5}}{2 \cdot 4}$

Multiply $- 16$ by $- 5$ .

$x = \frac{- 8 \pm \sqrt{64 + 80}}{2 \cdot 4}$

Add $64$ and $80$ .

$x = \frac{- 8 \pm \sqrt{144}}{2 \cdot 4}$

Rewrite $144$ as $12^{2}$ .

$x = \frac{- 8 \pm \sqrt{12^{2}}}{2 \cdot 4}$

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

$x = \frac{- 8 \pm 12}{2 \cdot 4}$

Multiply $2$ by $4$ .

$x = \frac{- 8 \pm 12}{8}$

Simplify $\frac{- 8 \pm 12}{8}$ .

$x = \frac{- 2 \pm 3}{2}$

Step 4

The final answer is the combination of both solutions.

$x = \frac{1}{2}, - \frac{5}{2}$