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AQA A2 Mathematics MPC4 Core 4 - 9th June 2015 [Discussion & unofficial markscheme] watch

1. coordinates for C were (-9, -2, 18) ?
2. can someone explain question 1b? i got like 1/3ln5-1/6ln25 and i had no idea where to go from here. how did everyone got their solution? and does any one remember how many marks was it?
3. Some people are getting some weird answers for solving that DE, anyone else get c=5?
4. (Original post by I Persia I)
I did, can anyone else confirm?
Me too. But apparently the answer was actually 11/8? That's what a couple of my friends got.

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5. (Original post by kateyl)
Is it just me or I thought that the other coordinate for E (not the (11,0,0)) one didn't have a zero anywhere????
Sameee

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6. For the differential question: dr/dt= k/pir^2. But since we want it with respect to r, dt/dr = pir^2 / k, right?? I got 1/3. Seems logical since the rate was lower... at 0.5, as opposed to 4.5
7. (Original post by science33)
can someone explain question 1b? i got like 1/3ln5-1/6ln25 and i had no idea where to go from here. how did everyone got their solution? and does any one remember how many marks was it?
Turn the 25 into 5^2 and then use log rules to times the 2 by -1/6
8. (Original post by WillowXxx)
is it only me who didnt get 5. something for the other value of x on the Rcos(x+1.19) question? i got 3.34
no im the same! because it said 0<x<pi/2 so I don't know where people got 5 from?
9. (Original post by Hamzz9)
Me too. But apparently the answer was actually 11/8? That's what a couple of my friends got.

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Ahh dunno then, probably wrong :/
10. (Original post by science33)
can someone explain question 1b? i got like 1/3ln5-1/6ln25 and i had no idea where to go from here. how did everyone got their solution? and does any one remember how many marks was it?
1/6ln25 = 1/6ln5^2 = 2x1/6ln5 =1/3ln5
Should be 3ln5 Aswell
11. (Original post by I Persia I)
Ahh dunno then, probably wrong :/
Yeah think it was like (1+3/8)/(3/4 +1/4) = (11/8)/1 =11/8
12. (Original post by I Persia I)
Ahh dunno then, probably wrong :/
i got the same, just curious as to where abouts i went wrong lol
13. (Original post by science33)
can someone explain question 1b? i got like 1/3ln5-1/6ln25 and i had no idea where to go from here. how did everyone got their solution? and does any one remember how many marks was it?
Should have been 3ln5 - 1/6ln25 then ln25=2ln5 so 1/6ln25=2/6ln5 and 3ln5-2/6ln5= 8/3ln5
14. I weirdly enough got x=-3/4 and x=1/2 and I input the x value in inverse sin to get q? Out of 5 how many marks would that roughly get me
15. Can anyone remember the differential equation? Q8a

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16. (Original post by amyrah)
coordinates for c were (-9, -2, 18) ?
i got that
17. Hell .

Everyone's saying 5/256 for the binomials and I think I wrote 5/64, clearing having forgotten multiply by 1/4.
I didn't prove that h(x) is a decreasing function correctly (mind gamed myself to rewrite that answer).
I didn't finish the vectors question having skipped it after finishing a. to come back to later (almost finished b but not quite and no attempt on c) because I was checking my answers for the harder questions.

So... that's probably -1 mark (hopefully e.c.f for the estimate), -2 marks (scribbled out h'(x), like a boss), -2 marks (almost completing b. which I'm really annoyed about because it was easy) and -4 marks (no attempt at part c - anyone know what the question was as I didn't even read it?).

Which is -9 marks, putting me at 66. You guys think that will still be 90 ums? (I have probably ~96 ums in C3, accounting for any silly mistakes).
18. (Original post by George1231)
please try and add answers as I found the paper really hard and probably got a lot wrong
1) A=3 B=-1
b) 8/3ln5
2)a r=root 29 alpha=1.19
b)max value root 29
c)x=5.09x=0.568 or 5..72
3) d=1
b) (2x+1)(2x-1)(2x-3)c) h(x)=(1=2x)^-1 differentiate shows its decreasing
4a) 1+x-2x^2
b) 1/4 -x/16+5x^2/256
c)0.2313
b) equation of normal y=2x-1/2
c) x cooridinate -1/8
6a) 60 degrees
B) (15,3,2)
C) got wrong (11,0,0)
7a) 1/4-ln2
b)11/8
8a) x=9/20-1/2(t+1)-1/20(1+t)^2
b)dr/dt=k/pir^2
c) 3
Somehow i recognise most of these answers, put x=1/3 for binomial expansion but dont think i got 0.2313 which means i made a sign error somewhere. For the sin values last question i only remember getting 3.33 and something else for my two solutions, so not sure about that quesion. YESS I GOT -1/8 FOR Q. For question 8a) differential equation, they didnt ask for a specific from did they? I've seen papers where they leave it in a form that isnt x=f(x)
19. for 3C I put in multiple values of x above 2 to show that it is decreasing, would I get any marks?
20. (Original post by tiffanyyyyyyy)
For the differential question: dr/dt= k/pir^2. But since we want it with respect to r, dt/dr = pir^2 / k, right?? I got 1/3. Seems logical since the rate was lower... at 0.5, as opposed to 4.5
Nope, when something is inversely proportional it is always k/x. At you method of pir^2/k, the rate of change would increase as r increases - which is wrong

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