The slope-intercept form of a line is:
y = mx + b
where m is the slope and b the y-intercept.
The slope is computed as follows:

where (x1,y1) and (x2, y2) are two known points. Replacing with (4, -2) and (8, -9):

Replacing with the point (4, -2) and m = -7/4 into the general equation, we get:
-2 = (-7/4)4 + b
-2 = -7 + b
-2 + 7 = b
5 = b
Then, the equation is:
y = -7/4x + 5
The graph is