State Ranking (2 Viewers)

Continuum · Nov 24, 2008

shaon0 said:
his not that good lol.

shaon0 said:
And you know that how?

Timothy.Siu · Nov 24, 2008

youngminii · Nov 24, 2008

kurt.physics said:
1 x8 - a8 = (x4)2 - (a4)2
=(x4 - a4)(x4 + a4)
=((x2)2 - (a2)2)(x4 + a4)
=(x2 - a2)(x2 + a2)(x4 + a4)
=(x - a)(x + a)(x2 + a2)(x4 + a4)

kurt.physics said:
1 x10 - 1
= (x5)2 - 12
= (x5 - 1)(x5 + 1)

And thats as far as it goes

For the second one, i presume you mean this

(x^3/2)-(y^3/2) is x3/2 - y3/2

In which case, substituting ( (root x)2 and similarly with y) we get

= ((root x)2)3/2 - ((root y)2)3/2

= (root x)2 * 3/2 - (root y)2 * 3/2

= (root x)3 - (root y)3

Now we apply the difference of two cubes ( ie a2 - b2 = (a - b)(a2 + ab + b2) )

so,

x3/2 - y3/2 = (root(x) - root(y))(x +root(xy) + y)

P.S. Sorry about the lateness :S

kurt.physics said:
12 + 22 + 32 +...+ n2 = [n(n + 1)(2n + 1)] ÷ 6

First we see if its true for the most simplest case, n = 1

RHS = 1(1 + 1)(2 + 1) ÷ 6 = (1 * 2 * 3) ÷ 6 = 6 ÷ 6 = 1 = 12 = LHS

Then we assume its true for n = k. ie

12 + 22 + 32 +...+ k2 = [k(k + 1)(2k + 1)] ÷ 6

Now we prove its true for n = k + 1. ie

12 + 22 + 32 +...+ k2 + (k + 1)2 = [(k + 1)(k + 2)(2(k + 1) + 1)] ÷ 6

LHS = 12 + 22 + 32 +...+ k2 + (k + 1)2

Because we made the previous statement, we can sub this in to the k + 1 equation to see if it holds.

= ( [k(k + 1)(2k + 1)] ÷ 6 ) + (k + 1)2

= ( k(k + 1)(2k + 1) + 6(k + 1)2 ) ÷ 6 (making as one fraction)

= ( (k + 1)[ k(2k + 1) + 6(k + 1)] ) ÷ 6 (factoring k + 1)

= ( (k + 1)[ 2k2 + 7k + 6] ) ÷ 6

= ( (k + 1)(k + 2)(2k + 3) ) ÷ 6 (factoring 2k2 + 7k + 6 [check yourself if you like])

=RHS (this can be show by subing the k + 1 into the original formula)

Then you write a conclusive statement like; we have shown this to be true for k + 1, therefore it is true for all integers. Or whatever (i dont have textbook beside me)

Thats it

Now I know they're not over-the-top, extremely hard question but this kid's in year 9

friction · Nov 24, 2008

Y do people do that. Do yr 12 when ur in yr 12 noone really cares how u go in the HSC anyway.

youngminii · Nov 24, 2008

friction said:
Y do people do that. Do yr 12 when ur in yr 12 noone really cares how u go in the HSC anyway.

People do that 'cause they're exceptionally good or enjoy maths. Accelerating also relieves the workload in year 12, making it easier to get a higher UAI (by splitting the workload into 2 years)

shantu1992 · Nov 24, 2008

回复: Re: State Ranking

bendha said:
at least 80+ and top in your school .. i don't think 81 will be enough, 3U is way easier than 4U

i got 69%(which they are goign to change to 100%-they took marks off me for not putting log e's when basically everythign else was right) for 3 unit
and 98% for 4 unit
does that mean i have a chance of a state ranking

haaha nahh doubt it aye, prob will in economics though
heaps of competition from north sydney boys in economics though
and some of the provate schools knox, grammar

addikaye03 · Nov 25, 2008

youngminii said:
Now I know they're not over-the-top, extremely hard question but this kid's in year 9

Is that guy really in yr 9? i read his sig and thought it musta been bullshit..Hes very good for his age.

Zephyrio · Nov 25, 2008

youngminii said:
People do that 'cause they're exceptionally good or enjoy maths. Accelerating also relieves the workload in year 12, making it easier to get a higher UAI (by splitting the workload into 2 years)

Acceleration does relieve the workload in year twelve, but I would contend with the fact that it acceleration thereby increases your UAI. Sure, for some exceptionally talented kids, they can get state rankings in year 11. But for the vast majority, the marks accelerated kids get are not what they would have achieved had they taken their HSC in that subject a year later. Take namu for example. He said that he can't get a state rank in 3U this year (he's accelerated) but come this time next year, he'll be talking about a state ranking in it for sure. And as to which of these two (at this point, hypothetical) marks would boost the UAI, surely the latter...

tommykins · Nov 25, 2008

gurmies said:
tommykins,I could say the same about your mind =D I don't think i've ever seen you get a question wrong. Moreover, I haven't ever seen you post up a query of your own That's saying something

Eh, I tend to be able to do most questions but silly mistakes here and there fuck me up.

I rarely ask questinos because the questions others ask is enough practice for me

addikaye03 said:
Tommykins is very good at maths, but i believe lolokay shows a certain uniqueness when answering the Q. I mean, i consider myself pretty good at maths as you all are ( and im sure u think the same bout urself lol) but hes freaky. Have a look through some of his posts if u dont think so, i really cant see a Q he wont answer. Probability screws me over most times ( harder Q) but he rapes them lol

lolokay > me by far

dp624 · Dec 7, 2008

Timothy.Siu said:
they dont and they wont

I'm pretty sure ruse would get a few (2/3?)

lyounamu · Dec 7, 2008

lol wtf

I haven't come back to this thread for a long time.

Of course, I cannot be compared to lolokay. He is one of the top mathematician out here. It's a pity that he didn't do Maths olympiad.

So let's close this case (of comparing people) and shall we move on?

Back on topic: so does everyone reckon we will see many state ranks from JRAGH for 3 unit maths?

dp624 · Dec 7, 2008

Well last year it was like 1234 then 55555555
so i think maybe the cut off was 82 for state rank?
Probably around the same this year then

lyounamu · Dec 7, 2008

dp624 said:
Well last year it was like 1234 then 55555555
so i think maybe the cut off was 82 for state rank?
Probably around the same this year then

Last year one was really easy. But this one was a little bit harder.

That's just my opinion...

shaon0 · Dec 7, 2008

lyounamu said:
Last year one was really easy. But this one was a little bit harder.

That's just my opinion...

It was a little harder but there are so many ppl really good at maths out there. So i think it'll be around the same mark.

lyounamu · Dec 7, 2008

shaon0 said:
It was a little harder but there are so many ppl really good at maths out there. So i thikn it'll be around the same mark.

You didn't even take the HSC exam for 3 Unit so you don't know.

I have taken that test along with 20+ past papers before that. I also have great number of people at my own school and at other school saying that this exam was harder. It's not just my own opinion and I have also asked "ppl really good at maths".

Trebla · Dec 7, 2008

Even if it was hard, there are almost always people out there who get 100. The 2006 paper was considered "hard" and many still managed 100.

dp624 · Dec 7, 2008

But that 100 does not equate a 100% (84/84), it's only moderated htat way.

Trebla · Dec 7, 2008

It sometimes does. There is a high probability of it happening as well and it's definitely happened before with no clear correlation with the difficulty of the exam. So there's definitely a good chance someone or some people may get full marks this year. If the top end did not get full marks or at least very close to it, then there would be no 100 score given out (which happened in the 2 unit HSC 2006).

dp624 · Dec 7, 2008

AFAIK both 83 and 84 would get a moderated 100, unless there is like 5 people or more on 84. TBH i don't see more than 4 on 84 so yea.
I don't think you even know what the top mark was each year (for all you know it could be like 53/84 or something haha - just that it gets moderated to 100)

shaon0 · Dec 7, 2008

lyounamu said:
You didn't even take the HSC exam for 3 Unit so you don't know.

I have taken that test along with 20+ past papers before that. I also have great number of people at my own school and at other school saying that this exam was harder. It's not just my own opinion and I have also asked "ppl really good at maths".

lol. Good work, Lyounamu. You mustn't have talked to many of them.

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