Solve Using the Quadratic Formula 2x^2-7x=15

$2 x^{2} - 7 x = 15$

Step 1

Subtract $15$ from both sides of the equation.

$2 x^{2} - 7 x - 15 = 0$

Step 2

Use the quadratic formula to find the solutions.

$\frac{- b \pm \sqrt{b^{2} - 4 (a c)}}{2 a}$

Step 3

Substitute the values $a = 2$ , $b = - 7$ , and $c = - 15$ into the quadratic formula and solve for $x$ .

$\frac{7 \pm \sqrt{{(- 7)}^{2} - 4 \cdot (2 \cdot - 15)}}{2 \cdot 2}$

Step 4

Simplify.

Simplify the numerator.

Raise $- 7$ to the power of $2$ .

$x = \frac{7 \pm \sqrt{49 - 4 \cdot 2 \cdot - 15}}{2 \cdot 2}$

Multiply $- 4 \cdot 2 \cdot - 15$ .

Multiply $- 4$ by $2$ .

$x = \frac{7 \pm \sqrt{49 - 8 \cdot - 15}}{2 \cdot 2}$

Multiply $- 8$ by $- 15$ .

$x = \frac{7 \pm \sqrt{49 + 120}}{2 \cdot 2}$

Add $49$ and $120$ .

$x = \frac{7 \pm \sqrt{169}}{2 \cdot 2}$

Rewrite $169$ as $13^{2}$ .

$x = \frac{7 \pm \sqrt{13^{2}}}{2 \cdot 2}$

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

$x = \frac{7 \pm 13}{2 \cdot 2}$

Multiply $2$ by $2$ .

$x = \frac{7 \pm 13}{4}$

Step 5

The final answer is the combination of both solutions.

$x = 5, - \frac{3}{2}$