Solve Using the Quadratic Formula x^2-18x+71=0

$x^{2} - 18 x + 71 = 0$

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 $a = 1$ , $b = - 18$ , and $c = 71$ into the quadratic formula and solve for $x$ .

$\frac{18 \pm \sqrt{{(- 18)}^{2} - 4 \cdot (1 \cdot 71)}}{2 \cdot 1}$

Step 3

Simplify.

Simplify the numerator.

Raise $- 18$ to the power of $2$ .

$x = \frac{18 \pm \sqrt{324 - 4 \cdot 1 \cdot 71}}{2 \cdot 1}$

Multiply $- 4 \cdot 1 \cdot 71$ .

Multiply $- 4$ by $1$ .

$x = \frac{18 \pm \sqrt{324 - 4 \cdot 71}}{2 \cdot 1}$

Multiply $- 4$ by $71$ .

$x = \frac{18 \pm \sqrt{324 - 284}}{2 \cdot 1}$

Subtract $284$ from $324$ .

$x = \frac{18 \pm \sqrt{40}}{2 \cdot 1}$

Rewrite $40$ as $2^{2} \cdot 10$ .

Factor $4$ out of $40$ .

$x = \frac{18 \pm \sqrt{4 (10)}}{2 \cdot 1}$

Rewrite $4$ as $2^{2}$ .

$x = \frac{18 \pm \sqrt{2^{2} \cdot 10}}{2 \cdot 1}$

Pull terms out from under the radical.

$x = \frac{18 \pm 2 \sqrt{10}}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{18 \pm 2 \sqrt{10}}{2}$

Simplify $\frac{18 \pm 2 \sqrt{10}}{2}$ .

$x = 9 \pm \sqrt{10}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$x = 9 \pm \sqrt{10}$

Decimal Form:

$x = 12.16227766 \dots, 5.83772233 \dots$