Solve Using the Quadratic Formula x^2-x=56

$x^{2} - x = 56$

Step 1

Subtract $56$ from both sides of the equation.

$x^{2} - x - 56 = 0$

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 $a = 1$ , $b = - 1$ , and $c = - 56$ into the quadratic formula and solve for $x$ .

$\frac{1 \pm \sqrt{{(- 1)}^{2} - 4 \cdot (1 \cdot - 56)}}{2 \cdot 1}$

Step 4

Simplify.

Simplify the numerator.

Raise $- 1$ to the power of $2$ .

$x = \frac{1 \pm \sqrt{1 - 4 \cdot 1 \cdot - 56}}{2 \cdot 1}$

Multiply $- 4 \cdot 1 \cdot - 56$ .

Multiply $- 4$ by $1$ .

$x = \frac{1 \pm \sqrt{1 - 4 \cdot - 56}}{2 \cdot 1}$

Multiply $- 4$ by $- 56$ .

$x = \frac{1 \pm \sqrt{1 + 224}}{2 \cdot 1}$

Add $1$ and $224$ .

$x = \frac{1 \pm \sqrt{225}}{2 \cdot 1}$

Rewrite $225$ as $15^{2}$ .

$x = \frac{1 \pm \sqrt{15^{2}}}{2 \cdot 1}$

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

$x = \frac{1 \pm 15}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{1 \pm 15}{2}$

Step 5

The final answer is the combination of both solutions.

$x = 8, - 7$