write y=x^2-2x-8 in intercept form. then find the x-intercept and the vertex

Guest Apr 3, 2017

#1**+2 **

It's easier to find the x intercepts by factoring x^2 - 2x - 8 and setting y = 0

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

And setting both of the factors to 0 and solving for x, we have that x = 4 and x = -2

To find the vertex :

y=x^2-2x-8 complete the square on x

y = x^2 - 2x + 1 - 8 - 1 factor the first three terms

y = (x - 1)^2 - 9

And the vertex is ( 1, - 9)

Here's the graph : https://www.desmos.com/calculator/pqqn4ceovc

CPhill
Apr 3, 2017