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
 = \sqrt{x + 11})
with respect to x from
to
. [4 marks]"
My attempt to answer:
 = \sqrt{5 + 11})
 = \sqrt{16})
 = 4 )
 = \sqrt{5 + h + 11})
 = \sqrt{16 + h})
 = 4 + \sqrt{h})
*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
 = 4)
.
I can sub in 20 for h:
 = \sqrt{5 + 20 + 11} )
 = \sqrt{36})
 = 6 )
Run that through the slope formula:
Then, using my average rate of change thing:
![\frac{\sqrt[h]][h]]](http://latex.codecogs.com/png.latex?\frac{\sqrt[h]][h]])
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???
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which I think is different, please correct me, I am so confused.
Originally Posted by Kakariki 
