Sequences And Series Part C)

orangetictac

Is there anyone who know they have the right answer??:pac::pac::p:p

titan18

For what part?And whats the question

raah!

I'm pretty sure I got it right...... but I can't remember the exact answer, along the lines of "n cubed + 3 n squared + something + something + 2 to the power of n+1 + something"

I'm sure that's very helpful

titan18

Is this OL or HL

orangetictac

q4c)

did u do the test today?

its http://www.examinations.ie/archive/exampapers/2008/LC003ALP100EV.pdf

orangetictac

Looks like no one did it?:eek:

titan18

I do Ol so I'm no use to you

raah!

I did it. Here's the unexpanded version that you can tell from just looking at it

6 X n/6(2n+1)(n+1) +2X n/2(n+1) + 5n +2(2(to the power of n)-1)

orangetictac

raah! wrote: »

I did it. Here's the unexpanded version that you can tell from just looking at it

6 X n/6(2n+1)(n+1) +2X n/2(n+1) + 5n +2(2(to the power of n)-1)

Thanks raah!
Thats wat i got in the exam 2!
Wasnt gonna do s&s until i decided 2 look over the formula at 11 last night.
Lucky i did. nice question

eoin2nc

For the (2 to the power of r) did you just have to treat it like the sum to N of a geometric?

ShogunWarrior

First I wrote 2^r as 2^( (n/2)(n+1) ) but that made no sense then wrote out the series 2^1, 2^2, 2^3, 2^4 etc... so a=2, r=2 and using a(1-r^n)/1-r you get what's above

orangetictac

eoin2nc wrote: »

For the (2 to the power of r) did you just have to treat it like the sum to N of a geometric?

Ya thats wat i did:pac:

ShogunWarrior

Hey I've done out Q4 (c) (ii) here, hopefully it's right, looking at others' answers most of it is anyway

Attached PDF of the answer done out.

orangetictac

Would they take a mark off if you left it as 2.2(to the power of n) instead of 2(to the power of 1+n) at the end?:cool:

ShogunWarrior

I don't think so really, I know it could be B(-3) maybe for not finishing but looking at the marking scheme for 2001 Q4 (c) (ii) which is a similar question there is no explicit blunders noted for not finishing etc., hopefully not

eoin2nc

orangetictac wrote: »

Ya thats wat i did:pac:

Thats good to hear. I wasn planning on doing Q4 until Q8 turned out to be impossible, well IMO