Answer:
a) t(n) = 200n -238
b) t(n) = 2.7n -4.3
Explanation:
This is the same sort of problem as writing the equation of a line through two points. The slope (coefficient of n) is found using the slope formula:
m = (y2 -y1)/(x2 -x1)
And the constant term is found from one point and the slope:
b = y1 -m·x1
As always, if you have a number of these to do, you can save some trouble by putting the formulas in a spreadsheet. It will guarantee the formula is executed without mistakes.
In the attached, we have labeled the points (n1, t1), (n2, t2) instead of (x1, y1) and (x2, y2).
__
a) t(n) = 200n -238
b) t(n) = 2.7n -4.3