We are given the following function

We are asked to find the average rate of change for the above function in the interval [-3, -1]
The average rate of change for a function is given by

For the given case, the interval is [a, b] = [-3, -1]
This means that a = -3 and b = -1
Let us evalute the function at a = -3 and b = -1

So, we have
f(-3) = f(a) = 6
f(-1) = f(b) = -10

Therefore, the average rate of change for the function is -8 in the interval [-3, -1]