-x-1
all you do is subtract 9x from 8x.
It looks like your question is incomplete. I believe you also have options to pick which graph is correct. However, I can still give you the information you are looking for.
The slope of the line is -1.2
The Y-intersect is (0, 4)
I have also attached an image of what the graph would look like.
Hope this helps.
6^2 = x (x - 9)
x^2 - 9x - 36 = 0
(x -12)(x + 3) = 0
x - 12 = 0; x = 12
x +3 = 0; x = -3
so in this case x = 12 then DC = 12 - 9 = 3
y^2 = 12^2 - 6^2
y^2 = 144 - 36
y^2 = 108
y = 10.4