Question

How would I solve this?

Answer 1

start by rewriting the function in index form

\[f(x) = \frac{-9}{x}~~~~or~~~~~f(x) = -9x^{-1}\]

now you can find the derivative

when you get the derivative just substitute x =12 and calculate an answer

Answer 2

or if you wait someone always gives the answer

Answer 3

Thanks.

Answer 4

Well how do I find the derivative, I'm not familiar with the process.

Answer 5

@campbell_st

Answer 6

ok... well if you don't understand the process of differentiation, then it's extremely difficult to complete this question.

so have you studied any calculus..?

Answer 7

I do not understand differentiation that well, as I am self taught.

Answer 8

ok, well here are some good online notes that take you through the process and methods

but the basic thing for your question, now it's rewritten is to use this

if \[f(x) = ax^n\]

then the derivative is

\[f'(x) = n \times ax^{n -1}\]

here are the notes

http://tutorial.math.lamar.edu/Classes/CalcI/DerivativeIntro.aspx

hope they help

Answer 9

Thanks, you've been very helpful.

Answer 10

@campbell_st

Answer 11

I think it is 1/16 is that correct?

Answer 12

that's correct

Answer 13

Thanks :)