/sci/ - Science & Math » Thread #13122794

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finding nth term

Anonymous Thu 13 May 04:21:08 2021 No.13122794 View Reply Original Report

Quoted By: >>13122839 >>13123003 >>13123269 >>13124110 >>13124802

hi /sci/, i feel retarded for not knowing high school math, but i need help with this problem.

Given a sequence, the first term is 3 and each term after is one less than three times the previous term. so like 3, 8, 23,68...
how can i create an equation to finding the nth term? so if i want to know the 10th term what do i do?

Anonymous

Anonymous Thu 13 May 2021 04:36:06 No.13122839 Report

Quoted By: >>13122849

>>13122794
you should pay one of your nerd faggot friend to solve it

Anonymous

Anonymous Thu 13 May 2021 04:37:45 No.13122849 Report

Quoted By: >>13123648

>>13122839
but you guys are my friends..

Anonymous

Anonymous Thu 13 May 2021 04:49:30 No.13122898 Report

Quoted By: >>13122978

https://en.m.wikipedia.org/wiki/Arithmetico–geometric_sequence

Anonymous

Anonymous Thu 13 May 2021 05:20:46 No.13122978 Report

Quoted By:

>>13122898
i have no idea which part of that link explains my question. the examples in the link are totally different than my sequence.

Anonymous

Anonymous Thu 13 May 2021 05:30:35 No.13123003 Report

Quoted By: >>13123073 >>13123133 >>13124189 >>13124625

>>13122794
>3
>3(3)-1
>3(3(3) - 1) - 1
>3(3(3(3) - 1) - 1) - 1
>3(3(3(3(3) - 1) - 1) - 1) - 1
then do some algebra

Anonymous

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Anonymous Thu 13 May 2021 05:45:59 No.13123049 Report

Quoted By:

>>/g/81588065

Anonymous

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Anonymous Thu 13 May 2021 05:48:26 No.13123059 Report

Quoted By: >>13123073 >>13123155

>>>/g/81588065

Anonymous

Anonymous Thu 13 May 2021 05:55:46 No.13123073 Report

Quoted By: >>13123133

>>13123059
i don't have a python compiler but i don't see how what you wrote is any different from this guy>>13123003
the program just seems to loop N times instead of having an closed form expression.

Anonymous

Anonymous Thu 13 May 2021 06:13:38 No.13123116 Report

Quoted By: >>13123121

>maths doesn't have iteration notation
lemao

Anonymous

Anonymous Thu 13 May 2021 06:14:55 No.13123121 Report

Quoted By:

>>13123116
>what are summations
>what are ellipses
>what are recurrences

Anonymous

Anonymous Thu 13 May 2021 06:17:34 No.13123133 Report

Quoted By: >>13123153

>>13123073
>i don't see how what you wrote is any different from this guy>>13123003
>the program just seems to loop N times instead of having an closed form expressio
he didnt give you the close form because he has some faith that you can derive it. he told you the start of how to find it. you want to find a pattern in each term. its not hard.

Anonymous

Anonymous Thu 13 May 2021 06:22:16 No.13123153 Report

Quoted By: >>13123165

>>13123133
if you don't know the answer then don't pretend you know what you are talking about.

Anonymous

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Anonymous Thu 13 May 2021 06:22:55 No.13123155 Report

Quoted By: >>13125054

>>13123059

Anonymous

Anonymous Thu 13 May 2021 06:24:21 No.13123165 Report

Quoted By:

>>13123153
>NOOOOOOO SPOONFEED ME RIGHT NOW >:^(
youll probably still pass your shitty high school class anyways. enjoy your meaningless lazy brainlet life.

Anonymous

Anonymous Thu 13 May 2021 06:32:29 No.13123185 Report

Quoted By:

P_0 = 3
P_n = 3*p_(n-1) - 1

Anonymous

Anonymous Thu 13 May 2021 07:07:40 No.13123269 Report

Quoted By: >>13123322

>>13122794
5/6 3^n +1/2

Anonymous

Anonymous Thu 13 May 2021 07:25:02 No.13123322 Report

Quoted By: >>13124323 >>13124692 >>13125687

>>13123269
i don't need random answers without explanation.
i can just get the equation myself from Wolfram.

i want to know how the answer came about.

Anonymous

Anonymous Thu 13 May 2021 09:55:08 No.13123648 Report

Quoted By: >>13123658

>>13122849
Pay up

Anonymous

Anonymous Thu 13 May 2021 09:59:22 No.13123658 Report

Quoted By:

>>13123648
i wouldn't be here if i was rich.

Anonymous

Anonymous Thu 13 May 2021 13:07:22 No.13124110 Report

Quoted By:

>>13122794
Think of it with respect to indexing. You start off at the first term, which is 3, so your equation will have to keep that in mind. You then proceed to multiply this previous term by 3 and then subtract by one. It should be easy to formulate this if I've explained it well.

Anonymous

Anonymous Thu 13 May 2021 13:37:54 No.13124189 Report

Quoted By:

Here are three strategies which may work.
1. >>13123003 this
2. generating functions
3. diagonalization

Anonymous

Anonymous Thu 13 May 2021 14:34:22 No.13124323 Report

Quoted By: >>13124625

>>13123322
look up how to solve recurrence relations / difference equations, they are just differential equations in discrete time basically. it isn't hard to find a solution if it has a closed form but its annoying to remember the algorithm and much more convenient to throw it into wolfram,

Anonymous

Anonymous Thu 13 May 2021 16:13:13 No.13124625 Report

Quoted By:

>>13124323
you don't even need that level of math to solve this one. if you do this >>13123003
you can easily get an expression for each term and then simplify it to what you got by just applying the closed form formula for geometric partial sums and doing a bit of algebra.

Anonymous

Anonymous Thu 13 May 2021 16:25:02 No.13124692 Report

Quoted By:

>>13123322
>please do my homework
>nooo not just the answer, i need to show my work
pay attention in class next time or crack open the book. chances are its too late and your math hw is due today though so lmao get fucked

Anonymous

Anonymous Thu 13 May 2021 16:48:14 No.13124802 Report

Quoted By: >>13124808

>>13122794
a_n = 3^n - n, because you multiply by 3 n times and you subtract 1 n times

Anonymous

Anonymous Thu 13 May 2021 16:49:29 No.13124808 Report

Quoted By:

>>13124802
wrong

Anonymous

Anonymous Thu 13 May 2021 17:32:34 No.13125054 Report

Quoted By:

>>13123155
ooh massa

Anonymous

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Anonymous Thu 13 May 2021 18:54:11 No.13125445 Report

Quoted By:

f(n) = (3) (23/8)^n

Anonymous

Anonymous Thu 13 May 2021 19:36:46 No.13125687 Report

Quoted By: >>13125697

>>13123322
3
3^2 -1
3^3 - 3 -1
3^4 -3^2 -3 -1
$3^n - \sum\limits_{i=0}^{n-2}3^i = 3^n -1/6 * (3^n -3)$

Anonymous

Anonymous Thu 13 May 2021 19:38:07 No.13125697 Report

Quoted By:

>>13125687
btw I forgot to say you're fucking retarded and probably also black

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