Solve Using the Quadratic Formula 4x^2-5x-7=0

$4 x^{2} - 5 x - 7 = 0$

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 $a = 4$ , $b = - 5$ , and $c = - 7$ into the quadratic formula and solve for $x$ .

$\frac{5 \pm \sqrt{{(- 5)}^{2} - 4 \cdot (4 \cdot - 7)}}{2 \cdot 4}$

Step 3

Simplify.

Simplify the numerator.

Raise $- 5$ to the power of $2$ .

$x = \frac{5 \pm \sqrt{25 - 4 \cdot 4 \cdot - 7}}{2 \cdot 4}$

Multiply $- 4 \cdot 4 \cdot - 7$ .

Multiply $- 4$ by $4$ .

$x = \frac{5 \pm \sqrt{25 - 16 \cdot - 7}}{2 \cdot 4}$

Multiply $- 16$ by $- 7$ .

$x = \frac{5 \pm \sqrt{25 + 112}}{2 \cdot 4}$

Add $25$ and $112$ .

$x = \frac{5 \pm \sqrt{137}}{2 \cdot 4}$

Multiply $2$ by $4$ .

$x = \frac{5 \pm \sqrt{137}}{8}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$x = \frac{5 \pm \sqrt{137}}{8}$

Decimal Form:

$x = 2.08808748 \dots, - 0.83808748 \dots$