Question

If f is a function such that f(b)-f(a)/b-a=2, then which of the following statements must be true?

Answer 1

Based on the type of equation, f(b) relates to y2, f(a) relates to y1, b relates to x2, and a relates to x1.  If we change those around we now get:
(y2 - y1)/(x2 - x1) which is the slope formula, or the average rate of change.  thus your answer would be C