Integ Q (1 Viewer)

[krypticlemonjuice]

Why did they sub n = 3??

 

[SB257426]

Is it alright if you could show me the rest of the question as well please, I just need to have a look at the whole thing so I can a slightly more clear idea about the question,
thanks man

 

[howcanibesmarter]

From what u've given I'm assuming it's because if u subbed n<3 u get "negative" terms? I.e. for the 4th line if u use n=2 the I(n-3) will now be I(-1)? And 3 is the next number that works.

But yea SB257 is right you'll have to show the full part cus idk what a) iv) is asking for.

 

[krypticlemonjuice]

Oh, my bad, my bad

 

[howcanibesmarter]

I don't think it matters really, I used n=2 and u get the same.

 

[SB257426]

aha ! they haven't subbed in n=3 into the expression. They have applied a very clever trick here... give me a few minutes and ill send u my solution. They wanted you to understand how recurrence expressions actually work and ill show u in a bit

 

[SB257426]

so if you keep on using the In formula and continue to evaluate the In-k terms you notice a pattern:



Now if I evaluate In-4 and In-5 the same way I evaluated In-2 and In-3, I get:




And before anyone does say anything, I am aware that this question is only worth two marks but extension 2 course requires you to such heavy algebra.


Also lol, now that i think of it, its not really a trick but more of an observation.....

My teacher told me when we were learning this topic that some questions require you to go through the algebra..... if this topic were in an extension 1 paper easily be worth 3 marks

 

[SB257426]

Part v)

 

[howcanibesmarter]

My teacher told me when we were learning this topic that some questions require you to go through the algebra..... if this topic were in an extension 1 paper easily be worth 3 marks

would i get away w it if i jsut subbed in n=2 or is that not what the q wanted?

 

[synthesisFR]

would i get away w it if i jsut subbed in n=2 or is that not what the q wanted?

i dont think so u need to show its true for all cases so just follow the recurrence relation

 

[SB257426]

would i get away w it if i jsut subbed in n=2 or is that not what the q wanted?

Yeah the question wanted you to specifically follow the recurrence relationship and unfortunately just subbing in n=3 or n=2 would have gotten you only 1 mark for evaluating the integrals you obtained. The marker wants to make sure you know how the algebra behind this stuff works

 

[synthesisFR]

@krypticlemonjuice btw when is ur trials cuz ur grinding like mad

 

[krypticlemonjuice]

@krypticlemonjuice btw when is ur trials cuz ur grinding like mad

I should be grinding more man

My trials start next Friday so I haven't to much time left
Wby??

 

[synthesisFR]

I should be grinding more man

My trials start next Friday so I haven't to much time left
Wby??

tmrw

 

[krypticlemonjuice]

tmrw

Oh shi wtf, good luck mate

 

[synthesisFR]

Oh shi wtf, good luck mate

i will do my best