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C4 (Not MEI) - Thursday June 21 2012, PM

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Someone quicky explain why when you integrate 5/(x-5)^-1 it goes to ln(5-x) Not ln(x-5)?!?!?!
Its on june 09, just don't get it!

Because you can't ln a negative number. If you put them limits in it would be negative so you have to modulus it. If that makes any sense at all..........

Reply 421

Ouzo

Original post by Moi786

Because you can't ln a negative number. If you put them limits in it would be negative so you have to modulus it. If that makes any sense at all..........

Ahhh yeah, ok just about cheers.

Reply 422

cleverslacker

At least it's nearly over guys! good luck...

Original post by Moi786

To find the point of intersect you just have to do simulatenous equations with two vector equations. To find if they are parallel the directional vectors will be multiples of each other.

Danke

Reply 423

Sweetcorn_1

Just did the last piece of C4 revision I'll ever do, good luck guys, see you when you're done. I hope my mark is bloody good so I can balance out my M1 mark and get into UCL.

Reply 424

Ttawwab

FML. Bye Uni. :frown:

Reply 425

aware?

Original post by Ttawwab

FML. Bye Uni. :frown:

I know that feeling, very difficult paper.

Reply 426

Ttawwab

Original post by aware?

I know that feeling, very difficult paper.

Definitely one of the hardest C4 papers they've done.

What was up with that question 2: "Integrate ln(2+x)" or whatever it was. Pretty much no one I spoke to managed to do it. :frown:

Reply 427

aware?

Original post by Ttawwab

Definitely one of the hardest C4 papers they've done.

What was up with that question 2: "Integrate ln(2+x)" or whatever it was. Pretty much no one I spoke to managed to do it. :frown:

i tried to do it with integration by parts and got 0. lol

Reply 428

Matthew692692

Original post by Ttawwab

Definitely one of the hardest C4 papers they've done.

What was up with that question 2: "Integrate ln(2+x)" or whatever it was. Pretty much no one I spoke to managed to do it. :frown:

I thought it was ok but that question was horrible. I ended up with (ln(2+x))(x+2) -x.... I had no idea.

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Reply 429

etothepii

Am I the only one that thought it was a fairly nice paper? :confused:

Partial fraction integration (question 9) ln(16/5) - 1.5 anyone?
And the last part for question 10, I got something like a ratio of 3:2
For the first vector question, I got (13)^.5 for |a-b|

Reply 430

Azzza

Original post by Ttawwab

Definitely one of the hardest C4 papers they've done.

What was up with that question 2: "Integrate ln(2+x)" or whatever it was. Pretty much no one I spoke to managed to do it. :frown:

You had to use u=ln(2+x) and dv/dx=1 then use integration by parts. Took me a while to get my head round it.

The one I struggled with was getting question 4 into the form of y=f(x)

Overall I think it was an ok paper, but in comparison to previous papers it was certainly a little more challenging.

Reply 431

etothepii

As for integrating ln (x+2), I got xln(x+2) - x + ln(x+2)

Reply 432

Ttawwab

Original post by aware?

i tried to do it with integration by parts and got 0. lol

Haha, when I did parts I ended up trying to integrate x/(x+2) or something, so ridiculous.

Just moved onto the next one, saw it was a differential with tan(x) and e, and died inside. Ended up with an ln of an ln, fgs.

Reply 433

t4bz

sooo hard, thats my a in maths gone

Reply 434

Azzza

Original post by etothepii

Am I the only one that thought it was a fairly nice paper? :confused:

Partial fraction integration (question 9) ln(16/5) - 1.5 anyone?
And the last part for question 10, I got something like a ratio of 3:2
For the first vector question, I got (13)^.5 for |a-b|

I got the same as you in the partial fractions question and the first vector question. For the ratio I got root5:root17.

Reply 435

Starlight94

**** MY LIFE

This was posted from The Student Room's Android App on my GT-I9100

Reply 436

etothepii

Original post by Ttawwab

I got that too. You have to tweak it so you're integrating 1 - 2/(x+2), which you can then integrate.

Reply 437

goggy

I failed epically. :frown:

I didn't realise how to do 2) until about two minutes before the exam finished. I also missed out bits and bobs through it.

It's a good thing I don't need too many more marks to get my uni place AND I have M2 as well.

Reply 438

Sherlock.and.John

i got 13 for |a-b|… wasn’t entirely sure what to do. I thought it was also a nice paper until i looked on here and realised you had to integrate ln(2+x)! I just differentiated it by parts. Thought it was too easy :redface:

Reply 439

Matthew692692

Original post by etothepii

Am I the only one that thought it was a fairly nice paper? :confused:

Partial fraction integration (question 9) ln(16/5) - 1.5 anyone?
And the last part for question 10, I got something like a ratio of 3:2
For the first vector question, I got (13)^.5 for |a-b|

I got 2:3 ratio! Didn't have a clue on (13)^.5 for |a-b| can't remember q9

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C4 (Not MEI) - Thursday June 21 2012, PM

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