Solve Using the Quadratic Formula f(x)=x^2-8x

$f (x) = x^{2} - 8 x$

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 $a = 1$ , $b = - 8$ , and $c = 0$ into the quadratic formula and solve for $x$ .

$\frac{8 \pm \sqrt{{(- 8)}^{2} - 4 \cdot (1 \cdot 0)}}{2 \cdot 1}$

Step 3

Simplify.

Simplify the numerator.

Raise $- 8$ to the power of $2$ .

$x = \frac{8 \pm \sqrt{64 - 4 \cdot 1 \cdot 0}}{2 \cdot 1}$

Multiply $- 4 \cdot 1 \cdot 0$ .

Multiply $- 4$ by $1$ .

$x = \frac{8 \pm \sqrt{64 - 4 \cdot 0}}{2 \cdot 1}$

Multiply $- 4$ by $0$ .

$x = \frac{8 \pm \sqrt{64 + 0}}{2 \cdot 1}$

Add $64$ and $0$ .

$x = \frac{8 \pm \sqrt{64}}{2 \cdot 1}$

Rewrite $64$ as $8^{2}$ .

$x = \frac{8 \pm \sqrt{8^{2}}}{2 \cdot 1}$

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

$x = \frac{8 \pm 8}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{8 \pm 8}{2}$

Simplify $\frac{8 \pm 8}{2}$ .

$x = 4 \pm 4$

Step 4

The final answer is the combination of both solutions.

$x = 8, 0$