# OCR (not MEI) Core 3 - 19/01/2011 Watch

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#221

(Original post by

I didn't say it was wrong.

I was just showing them that 12*pi*ln(25)=24*pi*ln(5)

**ElMoro**)I didn't say it was wrong.

I was just showing them that 12*pi*ln(25)=24*pi*ln(5)

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#222

(Original post by

What did people actually get for the first question?

For reference the first question was: |3x + 4a| = 5a, where a is a positive constant.

I just did +- (3x+4a) =5a, and got 3x = a and -1/3x= a

**trix909**)What did people actually get for the first question?

For reference the first question was: |3x + 4a| = 5a, where a is a positive constant.

I just did +- (3x+4a) =5a, and got 3x = a and -1/3x= a

x = a/3 and x = -3a as a would probably be the constant and x is the variable. However, this would not lose you many marks.

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#223

(Original post by

Ok, I have just been sent a paper so will sort some answers out now. See you in half an hour!

**Mr M**)Ok, I have just been sent a paper so will sort some answers out now. See you in half an hour!

haha I wish I could to this in half an hour

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**Mr M**)

Ok, I have just been sent a paper so will sort some answers out now. See you in half an hour!

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#225

Question, and probably a stupid one at that. Everyone seems to have put that it was f(x) that had an inverse. I, being an idiot, forgot about e^x being the inverse of Lnx, so I worked out the inverse of g(x) instead. Thing is, it seemed to work. Anyone care to explain to me why that's not a valid inverse?

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(Original post by

Question, and probably a stupid one at that. Everyone seems to have put that it was f(x) that had an inverse. I, being an idiot, forgot about e^x being the inverse of Lnx, so I worked out the inverse of g(x) instead. Thing is, it seemed to work. Anyone care to explain to me why that's not a valid inverse?

**houseelf**)Question, and probably a stupid one at that. Everyone seems to have put that it was f(x) that had an inverse. I, being an idiot, forgot about e^x being the inverse of Lnx, so I worked out the inverse of g(x) instead. Thing is, it seemed to work. Anyone care to explain to me why that's not a valid inverse?

Like if you have x^2=4 you don't know if x=2 or x=-2.

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#227

**houseelf**)

Question, and probably a stupid one at that. Everyone seems to have put that it was f(x) that had an inverse. I, being an idiot, forgot about e^x being the inverse of Lnx, so I worked out the inverse of g(x) instead. Thing is, it seemed to work. Anyone care to explain to me why that's not a valid inverse?

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#228

(Original post by

g(x) had an x^2 in it so it isn't a one-to-one function there is no inverse.

Like if you have x^2=4 you don't know if x=2 or x=-2.

**ElMoro**)g(x) had an x^2 in it so it isn't a one-to-one function there is no inverse.

Like if you have x^2=4 you don't know if x=2 or x=-2.

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#229

balls! i forgot to write pi in the volume of revolution thing =[ (i always do that)

but all the answers ive seen here look familiar so otherwise im feeling good

but all the answers ive seen here look familiar so otherwise im feeling good

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#230

**houseelf**)

Question, and probably a stupid one at that. Everyone seems to have put that it was f(x) that had an inverse. I, being an idiot, forgot about e^x being the inverse of Lnx, so I worked out the inverse of g(x) instead. Thing is, it seemed to work. Anyone care to explain to me why that's not a valid inverse?

Needs To Be One-One To Define Its Inverse

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#231

Where has everyone got the answers from? Someone said they had just released the paper/answers?

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#232

(Original post by

Who has sen you the paper? So I can rep them aswell

**ElMoro**)Who has sen you the paper? So I can rep them aswell

(Thanks for the paper, how did you get it btw? )

P.S Shocking paper, I'll get 45/72 if Im generous :/

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#233

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#234

who did question 6i? i could not work out what dy/dx simplified to! i got

is this right? how would you simplify it?

edit: also, how many marks would i get for this working? the question is out of 4

is this right? how would you simplify it?

edit: also, how many marks would i get for this working? the question is out of 4

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#235

(Original post by

who did question 6i? i could not work out what dy/dx simplified to! i got

is this right? how would you simplify it?

**Princess_perfect786**)who did question 6i? i could not work out what dy/dx simplified to! i got

is this right? how would you simplify it?

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#236

(Original post by

Where has everyone got the answers from? Someone said they had just released the paper/answers?

***Lucy**)Where has everyone got the answers from? Someone said they had just released the paper/answers?

Being a teacher, respected member and frequent face in the Mathematics forums, his answers are trusted and appreciated

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#237

(Original post by

balls! i forgot to write pi in the volume of revolution thing =[ (i always do that)

but all the answers ive seen here look familiar so otherwise im feeling good

**godexists1234**)balls! i forgot to write pi in the volume of revolution thing =[ (i always do that)

but all the answers ive seen here look familiar so otherwise im feeling good

So if the question was worth 9, you should get a respectable 8

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#238

(Original post by

LOL WAT DOES EVERY THINK IS A JUSTIFIED OR LIKELY GRADE BOUNDARY FOR THIS EXAM?

personally i think an A could be 45/72

**nomzie**)LOL WAT DOES EVERY THINK IS A JUSTIFIED OR LIKELY GRADE BOUNDARY FOR THIS EXAM?

personally i think an A could be 45/72

Everyone said they found it hard but looks like theyve all got the right answers unlike me :\

Just looked at the answers and i would give myself about 46/ 72 and i was being generous!

Bloody brilliant, needed an A as well

Hello retake!

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#240

Made a right mess up of that exam. Need an A* for my uni offer as well so looks like a resit is in order. Hopefully they'll lower the boundaries though :/

Got the Cot(o) = 4 question entirely wrong, and the very last Q, last part I made a stupid error (forgot to sub the x-value back in to get the range). Also think I've got one of the G(x) F(X) questions wrong, the one where it was differentiate (lnX)^2 + 8 or something... I put 2lnX like an idiot...

So yeah, I'd guess that's what, 12 marks lost :/? Definitely no A* for me D:

Got the Cot(o) = 4 question entirely wrong, and the very last Q, last part I made a stupid error (forgot to sub the x-value back in to get the range). Also think I've got one of the G(x) F(X) questions wrong, the one where it was differentiate (lnX)^2 + 8 or something... I put 2lnX like an idiot...

So yeah, I'd guess that's what, 12 marks lost :/? Definitely no A* for me D:

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