1. ## derivative question

Hi this should be easy but im having a bit of a brain block.

find the derivative of this with respect to x

-(x+1)(ln(y*z*r)

2. Originally Posted by stumped765
Hi this should be easy but im having a bit of a brain block.

find the derivative of this with respect to x

-(x+1)(ln(y*z*r)
Are $\displaystyle y, z$ and $\displaystyle r$ constants or are any of them functions of $\displaystyle x$?

3. they can be regarded as constants

4. Originally Posted by stumped765
Hi this should be easy but im having a bit of a brain block.

find the derivative of this with respect to x

-(x+1)(ln(y*z*r)
If $\displaystyle y, z, r$ are constants, then $\displaystyle \ln{(yzr)}$ is also a constant.

So $\displaystyle \frac{d}{dx}\left[-(x + 1)\ln{(yzr)}\right] = -\ln{(yzr)}$.

5. Originally Posted by Prove It
If $\displaystyle y, z, r$ are constants, then $\displaystyle \ln{(yzr)}$ is also a constant.

So $\displaystyle \frac{d}{dx}\left[-(x + 1)\ln{(yzr)}\right] = -x\ln{(yzr)}$.
Typo- that 'x' should not be in the final answer. This is simply -x C+ C (where I have written the constant ln(yzr) as "C"), linear in x, so its derivative is the constant -C= -ln(xzr).

6. Originally Posted by HallsofIvy
Typo- that 'x' should not be in the final answer. This is simply -x C+ C (where I have written the constant ln(yzr) as "C"), linear in x, so its derivative is the constant -C= -ln(xzr).
Yes, typo. Thanks.