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

0=(x-2)*(x+4)

Now set each factor equal to zero.

(x-2)=0
x=2

(x+4)=0
x=-4

The x-intercepts are (2,0) and (-4,0).