I am unsure as to which forum to put this in. I took a shot and put it here, apologies if wrong.

Okay, to the question I am having trouble with.

"Find the average rate of change of

with respect to x from

to

. [4 marks]"

My attempt to answer:

*I am unsure if I am correct in square rooting the 16, so having 4 + the square root of h.*

Then I use the

formula to get the slope of the secant *rate of change*:

That's my final solution. My problem with this solution is when I sub a number in for h, I get a different answer from running the numbers through, and simply going *square root of the number divided by the number*.

Example:

Let's pretend h is 20.

So I have

.

I can sub in 20 for h:

Run that through the slope formula:

Then, using my average rate of change thing:

I get:

which is a completely different answer. So I must be doing something wrong here.

Okay, I tried using 25 for h in the

and it gives the same ansewr as running the math through. So it is not technically h, but it is h + 5, so is this actually right???