Solve Using the Quadratic Formula 9x^2-x-2=0

$9 x^{2} - x - 2 = 0$

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 $a = 9$ , $b = - 1$ , and $c = - 2$ into the quadratic formula and solve for $x$ .

$\frac{1 \pm \sqrt{{(- 1)}^{2} - 4 \cdot (9 \cdot - 2)}}{2 \cdot 9}$

Step 3

Simplify.

Simplify the numerator.

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

$x = \frac{1 \pm \sqrt{1 - 4 \cdot 9 \cdot - 2}}{2 \cdot 9}$

Multiply $- 4 \cdot 9 \cdot - 2$ .

Multiply $- 4$ by $9$ .

$x = \frac{1 \pm \sqrt{1 - 36 \cdot - 2}}{2 \cdot 9}$

Multiply $- 36$ by $- 2$ .

$x = \frac{1 \pm \sqrt{1 + 72}}{2 \cdot 9}$

Add $1$ and $72$ .

$x = \frac{1 \pm \sqrt{73}}{2 \cdot 9}$

Multiply $2$ by $9$ .

$x = \frac{1 \pm \sqrt{73}}{18}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$x = \frac{1 \pm \sqrt{73}}{18}$

Decimal Form:

$x = 0.53022243 \dots, - 0.41911131 \dots$