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).#