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Urgent help for C3 exam tomorrow needed!

Hello,
Could anyone tell me how to do this question? I've looked at the mark scheme, but they've missed out steps. Question 3b in the image attached.
Thank-you! :smile:

ImageUploadedByStudent Room1402312306.820448.jpg

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Reply 1

maggiehodgson

Original post by bethmebob

Hello,
Could anyone tell me how to do this question? I've looked at the mark scheme, but they've missed out steps. Question 3b in the image attached.
Thank-you! :smile:

Posted from TSR Mobile

Use the substitution of u - denominator and see where you get from that.

Reply 2

GingerCodeMan

Original post by bethmebob

Hello,
Could anyone tell me how to do this question? I've looked at the mark scheme, but they've missed out steps. Question 3b in the image attached.
Thank-you! :smile:

Posted from TSR Mobile

Hint:

\displaystyle\int\frac{f'(x)}{f(x)}\,dx = \ln|f(x)| + c

, so see if there's a way you can get the top line to be the derivative of the bottom :smile:

(edited 9 years ago)

Reply 3

bethmebob

Hey guys, thanks for the help.
I'd managed to get that far, but then when looking at the mark scheme, it has taken out 1/6? I can't work out how they've done it?

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Reply 4

GingerCodeMan

Original post by bethmebob

Hey guys, thanks for the help.
I'd managed to get that far, but then when looking at the mark scheme, it has taken out 1/6? I can't work out how they've done it?

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What is the derivative of the denominator? And how would you change the numerator to get the denominator?

Reply 5

Old_Simon

Original post by bethmebob

Hey guys, thanks for the help.
I'd managed to get that far, but then when looking at the mark scheme, it has taken out 1/6? I can't work out how they've done it?

Posted from TSR Mobile

There is a big clue in part 1 of the q. You get that derivative first. Now in Part 2 you are looking for the numerator to be the derivative of the denominator. Well it is not but it is similar. Can you see the relationship and how 1/6 might come into it ?

Reply 6

Lookovertherez

Is the answer 1/6ln(91/5)?

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Reply 7

GingerCodeMan

Original post by Lookovertherez

Is the answer 1/6ln(91/5)?
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You can check your answers using WolframAlpha. The actual answer is here.

Reply 8

bethmebob

You're all fantastic, thank-you! This was actually for my friend, but she couldn't be bothered to create an account, so I let her to on mine. I'll forward on your responses and hopefully they'll be useful.
Thank-you again :smile:

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