2014 Extension 2 BOS Trial Exam Discussion Thread (3 Viewers)

[aDimitri]

most of them

well most of them are not to be taken seriously in the slightest

 

[seventhroot]

well most of them are not to be taken seriously in the slightest

never take the internet seriously

 

[Chlee1998]

Um who was the imo guy?

 

[Tugga]

Um who was the imo guy?

http://www.imo-official.org/country_individual_r.aspx?code=AUS

1/6 chance

But 'imo guy' said he skipped q14 and 15 and went straight to 16 so there's that...

 

[aDimitri]

http://www.imo-official.org/country_individual_r.aspx?code=AUS

1/6 chance

But 'imo guy' said he skipped q14 and 15 and went straight to 16 so there's that...

actually only 2 are in year 12 in NSW

 

[trapizi]

http://www.imo-official.org/country_individual_r.aspx?code=AUS

1/6 chance

But 'imo guy' said he skipped q14 and 15 and went straight to 16 so there's that...

OMG I sat next to this guy in the exam :|

 

[aDimitri]

so... when can we expect results?

 

[Trebla]

so... when can we expect results?

Someone's impatient

 

[aDimitri]

Someone's impatient

i care more about bos trials than HSC

 

[Trebla]

i care more about bos trials than HSC

Why?

 

[faisalabdul16]

Why?

HSC too ezzz for him

 

[aDimitri]

Why?

because i'm going to get my course fairly easily then never care about my HSC again. whereas i thoroughly enjoyed sitting this exam

 

[Carrotsticks]

so... when can we expect results?

Next Tuesday after paper 2 we will release 2U, 3U and 4U results.

 

[aDimitri]

Next Tuesday after paper 2 we will release 2U, 3U and 4U results.

thanks very much

 

[alficio]

Can someone help me with q10 multiple choice? I seriously have no clue

 

[glittergal96]

Can someone help me with q10 multiple choice? I seriously have no clue

The original question had a typo, so you had to actually calculate it. (I did it via differentiation of the geometric series formula, a trick you see later in the exam incidentally).

With multiple choice though, you can almost always do these types of questions by doing little tests. If we set n=2 and w=-1, the sum we get is 1+2(-1-1)=-3. The only answer that gives -3 at n=2 is D.

 

[Carrotsticks]

Can someone help me with q10 multiple choice? I seriously have no clue

The last option was supposed to be - 1-n.

This one was my fault. In the construction of the question, I summed two geometric series, one including w and another with w bar. I forgot though that I had to subtract 1 from both sides.

 

[glittergal96]

The last option was supposed to be - 1-n.

This one was my fault. In the construction of the question, I summed two geometric series, one including w and another with w bar. I forgot though that I had to subtract 1 from both sides.

Did you differentiate the geometric series formula or did you use some other trick for accounting for the linearly increasing coefficients? (The terms in the series being kz^{k-1}).

 

[Carrotsticks]

To get the closed form initially I used the standard differentiation trick, I think in Trebla's solutions he also used the sum of the sum of gp method. There's a third way I know of using (1-x)S(x) trick that handles it nicely.

 

[glittergal96]

To get the closed form initially I used the standard differentiation trick, I think in Trebla's solutions he also used the sum of the sum of gp method. There's a third way I know of using (1-x)S(x) trick that handles it nicely.

Ah yes, the differentiation and iterated sum methods were what came to mind, forgot about the (1-x)S(x) trick. I guess that reduces it to a GP, cool .