# F(x) substitution

1. Aug 29, 2008

### yoleven

1. The problem statement, all variables and given/known data
f(h+1)-f(h)/h. If f(x)=1/x, simplify.

2. Relevant equations

3. The attempt at a solution
1/x+1-(1/x)/h

is the answer 1/h? I am not sure if i substituted this correctly or if I solved this right.
I put 1/x in everywhere there was a f(h).

2. Aug 29, 2008

### Dick

If f(x)=1/x, then f(h+1)=1/(h+1), f(5)=1/5. Etc. x is only a dummy variable.

3. Aug 29, 2008

### rocomath

Incorrect.

f(h+1)=1/(h+1)

f(h)=1/h

[f(h+1)-f(h)]/h

[1/(h+1)-1/h]/h

Continue.

4. Aug 29, 2008

### yoleven

so it should have been (1/x+1 -1/x)/h
dealing with the numerator first, I bring the terms to a common denominator..
(x-x+1/x^2+x)/h.
i multiply the numerator by 1/h and get..
1/hx^2+hx
is that right?

5. Aug 29, 2008

### Dick

You aren't listening. There are NO x's in (f(h+1)-f(h))/h. Reread the previous posts. By the way, are you sure the problem isn't (f(h+1)-f(1))/h??

Last edited: Aug 29, 2008
6. Aug 29, 2008

### yoleven

Okay, I can see that now. Thanks.