# How do I find the x-intercepts of the graph of y=x^2+2x-8?

##### 1 Answer
Sep 13, 2014

The x-intercepts are the ordered pairs that have values of 0 for the y-values.

Various methods exist:

1) Graphing
2) Quadratic Formula
3) Factoring

Let's factor. The coefficient of the ${x}^{2}$ term is $1$ so we can look at the constant term, $- 8$, and find its factors that add up to, $2$, the coefficient of the $x$ term.

Factors of -8:

$1 + \left(- 8\right) = - 7$ , Does not work
$\left(- 1\right) + 8 = 7$ , Does not work
$2 + \left(- 4\right) = - 2$ , Does not work
$\left(- 2\right) + 4 = 2$ , Works because it is 2

$0 = \left(x - 2\right) \cdot \left(x + 4\right)$

Now set each factor equal to zero.

$\left(x - 2\right) = 0$
$x = 2$

$\left(x + 4\right) = 0$
$x = - 4$

The x-intercepts are $\left(2 , 0\right)$ and $\left(- 4 , 0\right) .$