Answer:
[f(1) - f(3)] / [1–3]
Explanation:
Formula
f(x) = 6(2.5)
How to find
The average rate of change over the interval [a,b], or the secant line between the points a and b on the function f(x), is [f(a) - f(b)]/[a-b]. So, substitute a for 1 and b for 3, and you get [f(1) - f(3)] / [1–3]. The quotient of that is your average rate of change.