# Thread: Help with Derivatives: Average and Instantaneous rate of change

1. ## Help with Derivatives: Average and Instantaneous rate of change

Hello, I am having some trouble solving this question:

Let f(x) = 2x^2 + 4x - 4

1) What is the average rate of change of "f " between x=5 and x=5.17?

I know the steps involved in how to find the average rate of change, but my final answers keeps coming out wrong.
I can get up to this step: 2(x+h)^2 + 4(x+h) - 4 / h
Im not sure if this step is right, or if I am messing up after this
Any help would be appreciated, thank you

2. Originally Posted by GholamiAnsari
Hello, I am having some trouble solving this question:

Let f(x) = 2x^2 + 4x - 4

1) What is the average rate of change of "f " between x=5 and x=5.17?

I know the steps involved in how to find the average rate of change, but my final answers keeps coming out wrong.
I can get up to this step: 2(x+h)^2 + 4(x+h) - 4 / h
Im not sure if this step is right, or if I am messing up after this
Any help would be appreciated, thank you
The average rate of change of "f" between x=5 and x=5.17 is $\displaystyle \displaystyle \frac{f(5.17)-f(5)}{0.17}$.