# How do you solve x^2 - 17x + 72 =0 using the quadratic formula?

Feb 26, 2016

Solution is $x = 9$ or $x = 8$

#### Explanation:

For equation $a {x}^{2} + b x + c = 0$, the solution given by quadratic formula is $\frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2 a}$.

To solve x^2−17x+72=0, we know that $a = 1$, $b = - 17$ and $c = 72$

Hence, solution is given by $\frac{- \left(- 17\right) \pm \sqrt{{\left(- 17\right)}^{2} - 4 \cdot 1 \cdot 72}}{2 \cdot 1}$ or

$\frac{17 \pm \sqrt{289 - 288}}{2}$ or $\frac{17 \pm 1}{2}$ or $\frac{17 + 1}{2}$ and $\frac{17 - 1}{2}$

Hence, solution is $x = 9$ or $x = 8$