Instead of doing your problem for you, I'll do one exactly in every detail
like yours so that you can do yours yourself using this as a model. You
won't learn it as well if I do it for you, so I'll do this one instead:
What is the average rate of change of y with respect to x over the interval
[–7, 3] for the function y = 4x + 1?
When x=-7 at the beginning of the interval [-7, 3],
y = 4x + 1 begins at y = 4(-7) + 1 = -28 + 1 = -27
When x=3 at the end of the interval [-7, 3],
y = 4x + 1 ends up at y = 4(3) + 1 = 12 + 1 = 13
So y has changed -27 to 13, which is a change of 13-(-27) = 13+27 = 40
And x has changed from -7 to 3, which is a change of 3-(-7) = 3+7 = 10
So the average rate of change of y with respect to x over the interval
[-7, 3] is given by
Now do yours exactly the same way.
Edwin