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OCR MEI C3 Mathematics June 2016 - Official Thread

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Original post by Cadherin
Yeah, I was a bit rushed... Will I get full marks on that part for correct coordinates and writing down y=0.5x without actually showing how I got it, as I didn't have time? :frown:


You might lose a method mark but you shouldn't lose any more than 1 I think :smile:
Original post by SuruthiG
very last q, about geometrical properties of f(x), what did you guys put

I said symmetrical about q so about the line X= 1/4lnk
Original post by jirapat121
yeah very sure because I did a paper yesterday and they asked the same question "prove that it was divisible by 3" and the mark scheme said to put odd x odd is divisible by 3


11*13=143

143 is not divisible by 3

so odd*odd=odd but isnt necessarily divisible by 3
Original post by Maligaha
Im pretty sure you have substituted 0 twice....IMG_20160621_112701.jpg



This is what I got
Original post by sonron202
This is what I got


Yessss... That's what I got too :smile:
[QUOTE="sonron202;65975579"]This is what I got[/QUOTE
Thank god people were making me nervous....
for geometrical properties it was symmetrical about the line 1/4lnk
Original post by Danny_L
I got k-1


yes same
Original post by mrk1357
11*13=143

143 is not divisible by 3

so odd*odd=odd but isnt necessarily divisible by 3


but I thought the equation was (2^n+1)(2^n-1) ?
Original post by Maligaha
Im pretty sure you have substituted 0 twice....IMG_20160621_112701.jpg


No just once that would be a crazy thing to do
Reply 170
Avatar for OD23
OD23
2
Cocked up the proof (although I probably got a decent amount of method marks) and the area question at the end but other than that it was a nice exam imo! Hopefully I didn't make too many stupid mistakes throughout the paper but I'm hoping for an A
Original post by Alexw1812
No just once that would be a crazy thing to do


It looks like you have....
Original post by jirapat121
but I thought the equation was (2^n+1)(2^n-1) ?

Yes, so 11 and 13 can't be produced by the equation. I am just saying that you can't prove it generally by saying odd*odd is always divisible by 3, because it is not. Here's what I did:

You had to factorise it to (2^n -1)(2^n +1).

If the remainder of (2^n -1) after dividing by 3 is zero, the whole thing clearly must be divisible.

If the remainder of (2^n -1) after dividing by 3 is 1, (2^n +1) must be divisible, so the whole thing must be divisible.

The remainder of (2^n -1) after dividing by 3 is never 2, because then 2^n would be divisible by 3, but it can't as it is a power of 2, so it can only be 1 or 0.
(edited 7 years ago)
Beautiful paper, 71/72 for me, lowest 68/72
This is what I remember:

Unparseable latex formula:

x^2n - 1\\[br](x^n - 1)(x^n + 1)



Odd * odd = odd so divisible by 3

Area = 19/12
ak+b = k-1
4ln(4)-4
Y=(1/2)x
Gradient = 8 question 3
dr/dt = 0.05 m per minute question 3ii
P=(-4, -2)
x = ln2 question 2
x=-1 and x=-1/3
dy/dx=1/(2cos2y)
Original post by Alexw1812
No just once that would be a crazy thing to do


It was k-1 because it was between 1/2lnk not 1/4lnk
Reply 175
Avatar for klefki
klefki
3
IMG_1929.JPG

I got 55/12 for the area in q8, can someone tell me where I went wrong please? (sorry it's sideways)
Original post by Crozzer24
Yeah I got something ln in it to, it was by parts and u was lnx so there must have been a ln in the answer.


No it was just 8 i got that
If anyone has any questions about the paper I'll answer them, fairly certain I got full marks so I'm happy to help out :smile:
Original post by daisyn97
consecutive odd numbers - one is a factor of 3, so product will be divisible by 3?


If you have 2 consecutive odd numbers, it is still possible that none of them is divisible by 3, like in the case of 11 and 13.

See my previous post for how you can prove it.
Original post by gemdarkstone
hmmm, i got -4ln4-4 (which i know realise should be 4ln+4...)
not sure who's right tho


No it should be 4ln4-4

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