Find the average rate of change of $y$ with respect to $x$ over the interval [3,5].
I did it $5=3^2+1$ =5
but the answer is 8
I think there must be formula for average rate of change but doesn't give the formula in the book.
Find the instantaneous rate of change of y with respect to $x$ at the point $x=-4$
I have no idea to start this question, the answer is =-8
Thanks in advance.