Solve Using the Quadratic Formula -4x^2-12x-9=0

$- 4 x^{2} - 12 x - 9 = 0$

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 $a = - 4$ , $b = - 12$ , and $c = - 9$ into the quadratic formula and solve for $x$ .

$\frac{12 \pm \sqrt{{(- 12)}^{2} - 4 \cdot (- 4 \cdot - 9)}}{2 \cdot - 4}$

Step 3

Simplify.

Simplify the numerator.

Raise $- 12$ to the power of $2$ .

$x = \frac{12 \pm \sqrt{144 - 4 \cdot - 4 \cdot - 9}}{2 \cdot - 4}$

Multiply $- 4 \cdot - 4 \cdot - 9$ .

Multiply $- 4$ by $- 4$ .

$x = \frac{12 \pm \sqrt{144 + 16 \cdot - 9}}{2 \cdot - 4}$

Multiply $16$ by $- 9$ .

$x = \frac{12 \pm \sqrt{144 - 144}}{2 \cdot - 4}$

Subtract $144$ from $144$ .

$x = \frac{12 \pm \sqrt{0}}{2 \cdot - 4}$

Rewrite $0$ as $0^{2}$ .

$x = \frac{12 \pm \sqrt{0^{2}}}{2 \cdot - 4}$

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

$x = \frac{12 \pm 0}{2 \cdot - 4}$

$12$ plus or minus $0$ is $12$ .

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

Multiply $2$ by $- 4$ .

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

Cancel the common factor of $12$ and $- 8$ .

Factor $4$ out of $12$ .

$x = \frac{4 (3)}{- 8}$

Cancel the common factors.

Factor $4$ out of $- 8$ .

$x = \frac{4 \cdot 3}{4 \cdot - 2}$

Cancel the common factor.

$x = \frac{4 \cdot 3}{4 \cdot - 2}$

Rewrite the expression.

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

Move the negative in front of the fraction.

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

Step 4

The final answer is the combination of both solutions.

$x = - \frac{3}{2}$ Double roots