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Mr M's OCR (not OCR MEI) Core 4 answers 18th January 2013

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For the integration by substitution (out of 7) how many marks do you think I'd get if I did everything correct but made a mistake integrating the second term? 4ish sound alright?
Original post by Hazofhorsham
For the integration by substitution (out of 7) how many marks do you think I'd get if I did everything correct but made a mistake integrating the second term? 4ish sound alright?


Might even be 5.
Original post by Mr M
Mr M's OCR (not OCR MEI) Core 4 answers 18th January 2013


1. 3xsin⁡(3x)+cos⁡(3x)9+k\frac{3x\sin(3x)+\cos(3x)}{9}+k (4 marks)


2. 27−72x+32x227-72x+32x^2 and ∣x∣<916|x|<\frac{9}{16} (5 marks)


3. dydx=2x−y22xy\frac{dy}{dx}=\frac{2x-y^2}{2xy}

Coordinates (1,2)(1, \sqrt{2}) and (1,−2)(1, -\sqrt{2}) (7 marks)


4. (i) Show intersection and (5, 4, 6) (5 marks)

(ii) 68.2 degrees (3 marks)


5. (i) (195,−35)(\frac{19}{5}, -\frac{3}{5}) (5 marks)

(ii) 4(x−2)2+9(1−y)2=364(x-2)^2 + 9(1-y)^2 = 36 (2 marks)


6. −23384-\frac{23}{384} (7 marks)


7. (i) Show ... (4 marks)

(ii) ln⁡(2+3)\ln (2+\sqrt3) (3 marks)


8. (i) Show ... (2 marks)

(ii) (321)+λ(03−1)\begin{pmatrix} 3 \\ 2 \\ 1 \end{pmatrix} + \lambda \begin{pmatrix} 0 \\ 3 \\ -1 \end{pmatrix} or any other correct equation (3 marks)

(iii) Show ... (1 mark)

(iv) Kite (1 mark)


9. (i) θ=−20+Ce−kt\theta = -20 + C e^{-kt} (3 marks)

(ii) k=120k=\frac{1}{20} and t = 22 minutes (5 marks)

(iii) k is greater in the second case (1 mark)


10. x−1+x+7x2−x−6x-1+\frac{x+7}{x^2-x-6} (4 marks)

(ii) 8+ln⁡(274)8+ \ln (\frac{27}{4}) (7 marks)


Thanks for the answers mr m..
Basicay, with 3, i got the correct answer but i didnt expand my brackets so i left it as((x-2)/3)2 +((1-y)/2)2, will i lose a mark for not simplifying even tho it never specified to?
Also with 9, in the first bit i forgot to put the constant, and in the second part, i got the wrong constant as i forgot to add 20 so ln40 was my c. My method is all right and my k is right 2. How many marks do you think i will lose? In these questions?
Everything else seems okay and ive worked out to have got like 59-60. Do you think thats an a?


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Original post by Coolina133
Thanks for the answers mr m..
Basicay, with 3, i got the correct answer but i didnt expand my brackets so i left it as((x-2)/3)2 +((1-y)/2)2, will i lose a mark for not simplifying even tho it never specified to?
Also with 9, in the first bit i forgot to put the constant, and in the second part, i got the wrong constant as i forgot to add 20 so ln40 was my c. My method is all right and my k is right 2. How many marks do you think i will lose? In these questions?
Everything else seems okay and ive worked out to have got like 59-60. Do you think thats an a?


Posted from TSR Mobile


The one you call 3) which is actually 5) is ok if that is an equation that is equal to 1 rather than the expression you posted.

Drop 3 marks on 9) overall?

I should think that is an A but no-one knows for sure at this stage.
Oh yeah and also in 3, i only got coordinates (1,root 2) as i didnt put +\- root 2.


Posted from TSR Mobile
Original post by Coolina133
Oh yeah and also in 3, i only got coordinates (1,root 2) as i didnt put +\- root 2.


Drop 1 or 2 depending on how the marks are allocated in the scheme.
Original post by Mr M
Drop 1 or 2 depending on how the marks are allocated in the scheme.


Thank you so much :smile:


Posted from TSR Mobile
Thanks Mr M :smile: One last question, on 7ii) I stated sec(x)=Cosx^-1, and subbed in Pi/3 and 0. But for some stupid reason I misread ln(cosx) as cosx the second time round so I got:

Ln(1+.5Root(3)) -ln(.5) -(ln1 -cos0)

Ln(1+.5root(3)) -ln(.5) -0 +1

Ln(2+root(3)) +1 and because we had to simplify to one log, I wrote:

Ln(2e +eRoot(3))

How many marks do you think I'll lose? 1,2 or all 3 of them?

Thank you
Hmmmm
I misread the formula book
I'm such idiot :l
So I did integration for sec^2 rather than sec
Do you reckon they will be benevolent and give me 1 Mark? T_T
I seems to lose 11 marks so probably have to retake in summer for A* Errrr!!

Thank you Mr M for the answers.
Reply 29
Avatar for MasonRP
MasonRP
would i get away with putting rhombus?? and i reckon about 90% hopefully ums will scale that up a little :P
Reply 30
Avatar for MasonRP
MasonRP
(Originally Posted by Coolina133)
Oh yeah and also in 3, i only got coordinates (1,root 2) as i didnt put +\- root 2.



i did the same i deliberately rules the second one out.. how annoying!
(edited 11 years ago)
Mr M, how many marks do you think I would lose if, on Q3, I had my equations right, but misread them as "y=2x" and then ended up with (1,2) and (-1,-2)?
Original post by MasonRP
would i get away with putting rhombus?? and i reckon about 90% hopefully ums will scale that up a little :P


No sorry.
Original post by jamesisenglish
Mr M, how many marks do you think I would lose if, on Q3, I had my equations right, but misread them as "y=2x" and then ended up with (1,2) and (-1,-2)?


Drop 2 marks?
Original post by Hazofhorsham
Thanks Mr M :smile: One last question, on 7ii) I stated sec(x)=Cosx^-1, and subbed in Pi/3 and 0. But for some stupid reason I misread ln(cosx) as cosx the second time round so I got:

Ln(1+.5Root(3)) -ln(.5) -(ln1 -cos0)

Ln(1+.5root(3)) -ln(.5) -0 +1

Ln(2+root(3)) +1 and because we had to simplify to one log, I wrote:

Ln(2e +eRoot(3))

How many marks do you think I'll lose? 1,2 or all 3 of them?

Thank you


I'm not sure you will get any more than 1 mark for that, sorry!
Original post by XingBairong
Hmmmm
I misread the formula book
I'm such idiot :l
So I did integration for sec^2 rather than sec
Do you reckon they will be benevolent and give me 1 Mark? T_T
I seems to lose 11 marks so probably have to retake in summer for A* Errrr!!

Thank you Mr M for the answers.


I don't think you will get a mark for that sorry!

And you are welcome.
Thank you :smile:
Reply 37
Avatar for jordantic
jordantic
Original post by Mr M
Mr M's OCR (not OCR MEI) Core 4 answers 18th January 2013


1. 3xsin⁡(3x)+cos⁡(3x)9+k\frac{3x\sin(3x)+\cos(3x)}{9}+k (4 marks)


2. 27−72x+32x227-72x+32x^2 and ∣x∣<916|x|<\frac{9}{16} (5 marks)


3. dydx=2x−y22xy\frac{dy}{dx}=\frac{2x-y^2}{2xy}

Coordinates (1,2)(1, \sqrt{2}) and (1,−2)(1, -\sqrt{2}) (7 marks)


4. (i) Show intersection and (5, 4, 6) (5 marks)

(ii) 68.2 degrees (3 marks)


5. (i) (195,−35)(\frac{19}{5}, -\frac{3}{5}) (5 marks)

(ii) 4(x−2)2+9(1−y)2=364(x-2)^2 + 9(1-y)^2 = 36 (2 marks)


6. −23384-\frac{23}{384} (7 marks)


7. (i) Show ... (4 marks)

(ii) ln⁡(2+3)\ln (2+\sqrt3) (3 marks)


8. (i) Show ... (2 marks)

(ii) (321)+λ(03−1)\begin{pmatrix} 3 \\ 2 \\ 1 \end{pmatrix} + \lambda \begin{pmatrix} 0 \\ 3 \\ -1 \end{pmatrix} or any other correct equation (3 marks)

(iii) Show ... (1 mark)

(iv) Kite (1 mark)


9. (i) θ=−20+Ce−kt\theta = -20 + C e^{-kt} (3 marks)

(ii) k=120k=\frac{1}{20} and t = 22 minutes (5 marks)

(iii) k is greater in the second case (1 mark)


10. x−1+x+7x2−x−6x-1+\frac{x+7}{x^2-x-6} (4 marks)

(ii) 8+ln⁡(274)8+ \ln (\frac{27}{4}) (7 marks)


DO you have the question paper?
Reply 38
Avatar for mitymiget
mitymiget
6
Original post by Mr M
Mr M's OCR (not OCR MEI) Core 4 answers 18th January 2013


1. 3xsin⁡(3x)+cos⁡(3x)9+k\frac{3x\sin(3x)+\cos(3x)}{9}+k (4 marks)


2. 27−72x+32x227-72x+32x^2 and ∣x∣<916|x|<\frac{9}{16} (5 marks)


3. dydx=2x−y22xy\frac{dy}{dx}=\frac{2x-y^2}{2xy}

Coordinates (1,2)(1, \sqrt{2}) and (1,−2)(1, -\sqrt{2}) (7 marks)


4. (i) Show intersection and (5, 4, 6) (5 marks)

(ii) 68.2 degrees (3 marks)


5. (i) (195,−35)(\frac{19}{5}, -\frac{3}{5}) (5 marks)

(ii) 4(x−2)2+9(1−y)2=364(x-2)^2 + 9(1-y)^2 = 36 (2 marks)


6. −23384-\frac{23}{384} (7 marks)


7. (i) Show ... (4 marks)

(ii) ln⁡(2+3)\ln (2+\sqrt3) (3 marks)


8. (i) Show ... (2 marks)

(ii) (321)+λ(03−1)\begin{pmatrix} 3 \\ 2 \\ 1 \end{pmatrix} + \lambda \begin{pmatrix} 0 \\ 3 \\ -1 \end{pmatrix} or any other correct equation (3 marks)

(iii) Show ... (1 mark)

(iv) Kite (1 mark)


9. (i) θ=−20+Ce−kt\theta = -20 + C e^{-kt} (3 marks)

(ii) k=120k=\frac{1}{20} and t = 22 minutes (5 marks)

(iii) k is greater in the second case (1 mark)


10. x−1+x+7x2−x−6x-1+\frac{x+7}{x^2-x-6} (4 marks)

(ii) 8+ln⁡(274)8+ \ln (\frac{27}{4}) (7 marks)

Hello Mr. M! How would you go about working out Question 9?
Reply 39
Avatar for souljarb
souljarb
Original post by mitymiget
Hello Mr. M! How would you go about working out Question 9?


does anyone have the question paper for OCR core 4 jan 2013.

Thanks in advance

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