Question 316882
y = x^2-7x-8


To find the x intercepts, simply set y=0 and solve for x (by factoring):
0=x^2-7x-8
0=(x-8)(x+1)


The x-intercepts are x=8 and x= -1.


The easiest way to graph it is to complete the square, to turn it into a form that is more easily graphed:


Completing the square:


y = x^2-7x-8       (halve the b term, -7, and then square it: (-7/2)^2 = 49/4)

y = x^2 -7x +49/4 - 8 - 49/4      (add 49/4 beside the b term, -7, but then subtract it after the -8 term)


y = (x - 7/2)^2 - 8 - 49/4
y = (x - 7/2)^2 - 81/4


So the vertex is at (7/2, -81/4)


It opens up (because the x^2 term is positive), and the line of symmetry is just the x-coordinate of the vertex, 7/2.


Hope that helps. Let me know if you're still stuck!