Answer:
Average rate of change(A(x)) of f(x) over a interval [a,b] is given by:

Given the function:

We have to find the average rate of change from x = 1 to x= 2
At x = 1
then;

At x = 2
then;

Substitute these in above formula we have;

⇒

therefore, average rate of change of the function f(x) from x = 1 to x = 2 is, -3.75