Solve Using the Quadratic Formula x^2-18x+70=0

$x^{2} - 18 x + 70 = 0$

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 $c = 70$ into the quadratic formula and solve for $x$ .

$\frac{18 \pm \sqrt{{(- 18)}^{2} - 4 \cdot (1 \cdot 70)}}{2 \cdot 1}$

Step 3

Simplify.

Simplify the numerator.

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

$x = \frac{18 \pm \sqrt{324 - 4 \cdot 1 \cdot 70}}{2 \cdot 1}$

Multiply $- 4 \cdot 1 \cdot 70$ .

Multiply $- 4$ by $1$ .

$x = \frac{18 \pm \sqrt{324 - 4 \cdot 70}}{2 \cdot 1}$

Multiply $- 4$ by $70$ .

$x = \frac{18 \pm \sqrt{324 - 280}}{2 \cdot 1}$

Subtract $280$ from $324$ .

$x = \frac{18 \pm \sqrt{44}}{2 \cdot 1}$

Rewrite $44$ as $2^{2} \cdot 11$ .

Factor $4$ out of $44$ .

$x = \frac{18 \pm \sqrt{4 (11)}}{2 \cdot 1}$

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

$x = \frac{18 \pm \sqrt{2^{2} \cdot 11}}{2 \cdot 1}$

Pull terms out from under the radical.

$x = \frac{18 \pm 2 \sqrt{11}}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{18 \pm 2 \sqrt{11}}{2}$

Simplify $\frac{18 \pm 2 \sqrt{11}}{2}$ .

$x = 9 \pm \sqrt{11}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$x = 9 \pm \sqrt{11}$

Decimal Form:

$x = 12.31662479 \dots, 5.68337520 \dots$