y=mx+b
m=(325-180)/(9-4)
m=145/5
m=29
y=29x+b, using point (4,180) we can solve for b
180=29(4)+b
180=116+b
64=b, so the line is:
y=29x+64
Now the standard form of a line is ax+by=c so:
-29x+y=64 (by convention the coefficient of x should be positive so)
29x-y=-64
...
We can use the point-slope form we found earlier...
f(x)=29x+64
...
This is just a line so you can use any two points to graph it.
Connect (1,93) to (2,122) and extend upward and to the right as far as you please. The x-axis should be labeled "days" and the y-axis as "dollars".
