The average r. of c. of a function f(x) on an interval [a,b] is:
f(b) - f(a)
--------------
b-a
You'll need to apply this to all four of the given functions.
First function: f(x) = x^2 + 3x
a= -2; b= 3
Then the ave. r. of c. for this function on this interval is:
18 - (-2) 20
------------------ = ---------- = 4. y increases by 4 for every unit increase in x.
3-(-2) 5
Do the same thing for the other 3 functions.
Then arrange your four results in descending order (greatest to least).