C1 MEI Wednesday 16th May 2012

dude (2K)^2 is 4K^2 though

Do you mean definitely correct answers?

also what did everyone get for the proof one? about odd numbers and what did you say about 'n'? I said that it has to be a multiple of 3 and a factor of 9 (but the last one is just a guess).

any idea what marks /72 will be 90ums?

Has to be a multiple of 3, not 1.5. I nearly put 1.5 but decided to stick with 3 - 4.5 is a multiple of 1.5
+ 9 gives 13.5 which isn't a multiple of 9.

Dangit!
Ok, reality check.

Lost 1 mark on 3i lost probably 2 for that on 7 lost one for not putting the x co-ordinate on 11(iii) and lost one for missing out one solution on 12ii

then maybe one more for a silly mistake somewhere

66/72 or 67/72, still 92/93 ums probably

Has to be a multiple of 3, not 1.5. I nearly put 1.5 but decided to stick with 3 - 4.5 is a multiple of 1.5
+ 9 gives 13.5 which isn't a multiple of 9.

i got something like B=-95.5 and C=167 or something like that. I put it into the equation and then put in f(2) during the exam and it worked so i think its right

pretty sure it said "when n is an integer"

i got that too!

The exact wording was:
"Given also that (n+3)^2-n^2 is divisible by 9, what can you say about n?"

I put 9/6, but he's right.

It says, "assuming n is an integer"; check the page before for the exact question.

Ah, I see....

I got B=-4 and C=-8 !

I swear it's stupid if the answer is 'it's divisible by 3".

Also, are we wrong? All multiples of 3 are multiples of 9/6, so it's actually right.

Does anyone know the grade boundaries please? My teacher said its 49/72 for a B and 55/72 for an A? x


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How does your teacher know this already? Is it a prediction?

You're wrong (even though, yes, 3 is a multiple of 1.5, but I don't think you'll get the marks for that). The answer IS, "it's a multiple of 3/2" because it has to be a multiple of 3 if it's a multiple of 9, you won't get marks for something so obvious, but look:

6n + 9 is divisible by 9, so cancel the 9:
6n HAS to be divisible by 9, so n is a multiple of 9/6 (3/2 = 1.5).

n may well be a 'multiple' of 1.5, but then it is also a multiple of 0.75, 0.5, etc!!!

When talking about multiples, it needs to be the smallest integer, so 3 is the correct answer.