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

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

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

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

Step 3

Simplify.

Simplify the numerator.

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

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

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

Multiply $- 4$ by $7$ .

$x = \frac{5 \pm \sqrt{25 - 28 \cdot - 4}}{2 \cdot 7}$

Multiply $- 28$ by $- 4$ .

$x = \frac{5 \pm \sqrt{25 + 112}}{2 \cdot 7}$

Add $25$ and $112$ .

$x = \frac{5 \pm \sqrt{137}}{2 \cdot 7}$

Multiply $2$ by $7$ .

$x = \frac{5 \pm \sqrt{137}}{14}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$x = \frac{5 \pm \sqrt{137}}{14}$

Decimal Form:

$x = 1.19319285 \dots, - 0.47890713 \dots$