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**BarandaMan****Guest**

i49.tinypic.com/ose3v5.jpg

Ok, as you can see, I did the first bit correct....

The second part with respect to Pi, I cannot get. I have spent over 75 minutes trying. I wrote it down all neat here and took a photo. Please, please, please can you show me in detail how to differentiate this? I am so bad at differentiation and it will really help.

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi BarandaMan;

I am sorry but I can not see that. It is showing up very dark on my browser.

I have so far:

that is all I can make out.

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**BarandaMan****Guest**

bobbym wrote:

Hi BarandaMan;

I am sorry but I can not see that. It is showing up very dark on my browser.

I have so far:

that is all I can make out.

Thank you! You are right so far!! The end is -1/yLi^y

I have differentiated with respect to Li correctly. The correct answer when differentiating with respect to Pi is on the sheet (let me know if you cannot see it). I cannot do it though, wrt Li I can do though!!

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

There is a capital y in the other term. Do you have Y and y?

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**Karimazer1****Guest**

Yes exactly, the little y is meant to be gamma so treated differently from the big Y!

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

So this is what we have:

You can expand that to:

The first two terms are just constants and disappear, you should be able to differentiate the next two terms wrt Pi.

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**BarandaMan****Guest**

I can do the fourth term as the Pi just dissappears right?

I have no idea how to use the chain rule here when there are fractions and powers like that, I've never seen a function like this before. Please can you help?

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

If you mean this term

Simplify it to:

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**BarandaMan****Guest**

bobbym wrote:

Hi;

If you mean this term

Simplify it to:

Thank you bobby, how/why does that rule work?

So Pi^-n * Pi = Pi^1-n? (With the divided by P excluded). Why does that work? How? Is this always the case?

Thanks

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

When you multiply like that you can add the powers provided the base is the same.

Yes, it is always the case.

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**BarandaMan****Guest**

Ok thank you for all your help bobby. I really cannot do this.

If anyone is willing to post a solution to the differentiation with respect to Pi, please let me know and explain. It may seem like I am not making an effort but I have, a lot, and me posting my working on here will be really unhelpful.

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

I can post a solution but I think you need some help with applying the power rule. We can go over it term by term...

This is the derivative with respect to Pi.

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**If it ain't broke, fix it until it is.**

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**BarandaMan****Guest**

bobbym wrote:

Hi;

I can post a solution but I think you need some help with applying the power rule. We can go over it term by term...

This is the derivative with respect to Pi.

Thanks. I have tried for days to work this out but I still do not understand this at all. Also, the P^2 on the bottom is inconsistent with the answer from the book. We want to differentiate only with respect to the Pi, not with respect to the 'P' on the bottom....this is completely different to the answer? Now I have two things I don't understand :P

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

For the next term let's simplify it a bit before differentiating

Is that clear to start?

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**If it ain't broke, fix it until it is.**

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**BarandaMan****Guest**

bobbym wrote:

Hi;

For the next term let's simplify it a bit before differentiating

Is that clear to start?

Yes! Thank you! That all makes sense, except for the last line, I don't know where the divided 'P' has gone?

**BarandaMan****Guest**

Basically I understand that Pi^-n bit, but not how ((Pi/P)^-n) / P gives P^ n-1?

So ((1/P)^-n )/ P ? I don't get how to manipulate this! Thank you bobbym.

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

When you have an expression like:

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**BarandaMan****Guest**

bobbym wrote:

Hi;

When you have an expression like:

Ok I know we haven't even started differentiating and I can't do this.

So (Pi^-n / P^-n) / P ... so the top stays the same... Pi^-n and the bottom I do not understand? Please can you just explain so I understand??:P It's taking me 5 days to do one question Maths is so difficult and I try so hard.

**BarandaMan****Guest**

Can someone just please explain why (Pi/P)^-n / P gives P^1-n... please someone?

**BarandaMan****Guest**

EDIT ^^ why it gives P^n-1..please someone this isn't even the question I wanted to solve in the first place and now I am stuck just simplifying things

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

please someone this isn't even the question I wanted to solve in the first place and now I am stuck just simplifying things

Simplifying is supposed to make things easier, it is part of math. Without it some problems are impossible.

It's taking me 5 days to do one question Maths is so difficult and I try so hard.

Pardon me for saying but you come in for 30 seconds and then I do not see you for 2 days. 5 x 30 seconds is 2 and half minutes of time spent on this problem. I could not solve it that quickly either. In order to get something out of this you have to spend the time in here with me, asking questions.

**In mathematics, you don't understand things. You just get used to them.**

**If it ain't broke, fix it until it is.**

**Online**

**BarandaMan****Guest**

bobbym wrote:

Hi;

please someone this isn't even the question I wanted to solve in the first place and now I am stuck just simplifying things

Simplifying is supposed to make things easier, it is part of math. Without it some problems are impossible.

It's taking me 5 days to do one question Maths is so difficult and I try so hard.

Pardon me for saying but you come in for 30 seconds and then I do not see you for 2 days. 5 x 30 seconds is 2 and half minutes of time spent on this problem. I could not solve it that quickly either. In order to get something out of this you have to spend the time in here with me, asking questions.

Ok. Thank you for your reply. That is a very helpful breakdown and it makes sense. I have been trying a lot but just keep getting nowhere so come back to ask questions. Sorry.

Ok, so I understand how to simplify the term, so now can we go from here?

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

Do you now see how this was done?

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**BarandaMan****Guest**

bobbym wrote:

Hi;

Do you now see how this was done?

Yes bobbym I fully understand this now! Thank you!

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 96,647

Hi;

Can you differentiate this wrt Pi?

It is just a power rule.

**In mathematics, you don't understand things. You just get used to them.**

**If it ain't broke, fix it until it is.**

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