# How do you solve  x^2-9x+8=0?

Mar 12, 2016

$x = 8 , 1$

#### Explanation:

color(blue)(x^2-9x+8=0

This is a Quadratic equation (in form $a {x}^{2} + b x + c = 0$)

color(brown)(x=(-b+-sqrt(b^2-4ac))/(2a)

Where

color(blue)(a=1,b=-9,c=8

Substitute the values in the formula

$\rightarrow x = \frac{- \left(- 9\right) \pm \sqrt{- {9}^{2} - 4 \left(1\right) \left(8\right)}}{2 \left(1\right)}$

$\rightarrow x = \frac{9 \pm \sqrt{81 - 32}}{2}$

$\rightarrow x = \frac{9 \pm \sqrt{49}}{2}$

$\rightarrow x = \frac{9 \pm 7}{2}$

Now, we have $2$ values for $x$

1)color(orange)(x=(9+7)/2

2)color(indigo)(x=(9-7)/2

Solve

1)color(green)(x=(9+7)/2=16/2=8

2)color(green)(x=(9-7)/2