# How do you solve x^2 - 6x + 9 = 0 using the quadratic formula?

Jul 10, 2016

x = 3

#### Explanation:

${x}^{2} - 6 x + 9 = {\left(x - 3\right)}^{2}$
There ia a double-root at x = 3

Using the formula as instructed.

Compare to: $a {x}^{2} + b x + c \to x = \frac{- b \pm \sqrt{{b}^{2} - 4 a c}}{2 a}$

In this case: a=1; b=-6 and c=9 giving:

$x = \frac{+ 6 \pm \sqrt{{\left(- 6\right)}^{2} - 4 \left(1\right) \left(9\right)}}{2 \left(1\right)}$

$x = \frac{6 \pm \sqrt{36 - 36}}{2}$

$x = 3 \pm 0$

$x = 3$