# Homework Help: Derivative of Fraction using power rule

1. Oct 2, 2011

### Phyzwizz

The problem:
f(x)=3-3/5x

So I'm perfectly fine with finding the derivatives with stuff but I wasn't sure about this one. Would this be 0 because there is a three in the numerator and no x?
Or would it be 3-1/51-1=3-1=2?

2. Oct 2, 2011

### Kreizhn

Sorry, is that $f(x) = 3 - \frac35 x$ or $f(x) = 3 - \frac3{5x}$?

3. Oct 2, 2011

### Windowmaker

f(x)=3−3/5x
The derivative of 3 is going to be zero because its a constant.
Bring the x to the numunator.

Then you get 3x^-1/5. Apply the power rule
You get:

(-1)3x^-1-1/5 = -3x^-2/5

Now rewrite with postive exponants:

f'(x)= 3/5x^2

4. Oct 2, 2011

### Phyzwizz

Thanks, that was pretty easy!

5. Oct 2, 2011

### Kreizhn

Hi Windowmaker. The point of these forums is to help guide people to the solution, not to do it for them.

6. Oct 2, 2011

### Windowmaker

I aplogize, im new here. I wont make that mistake in the future!

Last edited: Oct 2, 2011
7. Oct 2, 2011

### Kreizhn

No problem. I made that mistake when I was new too. Have fun and enjoy the forums.