# Thread: "Recursive definition"

1. ## "Recursive definition"

Does anybody know recursive definition?

What is recursive definition of the sequence a_n:
n = 1,2,3..... if

a) $a_n = 4n-2$
b) $a_n = 1+(-1)^n$
c) $a_n = n(n+1)$
d) $a_n = n^2$

Can anyone also explain me how he/she got the above answers!

2. Originally Posted by robocop_911
Does anybody know recursive definition?

What is recursive definition of the sequence a_n:
n = 1,2,3..... if

a) $a_n = 4n-2$
b) $a_n = 1+(-1)^n$
c) $a_n = n(n+1)$
d) $a_n = n^2$

Can anyone also explain me how he/she got the above answers!
a) a1 = 2, an = an-1 + 4

3. b) a1 = 0 an = |an-1 - 2|

4. Originally Posted by sean.1986
b) a1 = 0 an = |an-1 - 2|
Why are you in so needless hurry to reply!?

Anyways, you didn't give me any explanation about how you got the answers!

Also, can anyone check if whatever sean.1986 said is correct or not?

Seems like sean is a 22 year old guy.

5. Originally Posted by robocop_911
Why are you in so needless hurry to reply!?

Anyways, you didn't give me any explanation about how you got the answers!

Also, can anyone check if whatever sean.1986 said is correct or not?

Seems like sean is a 22 year old guy.
Why would you ever insult someoen who is helping you, that is just inappropriate

6. Hi !

For the first one for example, you can notice that $a_n=4n-2$ and $a_{n+1}=4(n+1)-2=(4n-2)+4=a_n+4$

So here is your recursive relation. Plus, for the first term, just replace n by 0 in $a_n$

7. Originally Posted by Mathstud28
Why would you ever insult someoen who is helping you, that is just inappropriate
I am not insulting anyone. Whenever I post a question I want it to be replied by well experienced people. Anyways, can you answer the questions and possibly give me an explanation?

8. Originally Posted by robocop_911
I am not insulting anyone. Whenever I post a question I want it to be replied by well experienced people. Anyways, can you answer the questions and possibly give me an explanation?
From what I have seen Sean is a fairly experienced student, and I would/could help you, but you see I am only 17, so I may not experienced enough for your liking, sorry

9. Originally Posted by robocop_911
I am not insulting anyone. Whenever I post a question I want it to be replied by well experienced people. Anyways, can you answer the questions and possibly give me an explanation?
You can be 22 years old and yet experienced...

But I quite agree that there is no point giving the full solution without any explanation, and it's quite rare that someone more wants the explanations than the solutions ^^

10. Originally Posted by Moo
Hi !

For the first one for example, you can notice that $a_n=4n-2$ and $a_{n+1}=4(n+1)-2=(4n-2)+4=a_n+4$

So here is your recursive relation. Plus, for the first term, just replace n by 0 in $a_n$

I am not getting any serious help here. Where are all the experienced guys? I really need to solve these sums!

11. Actually I'm 21. I was in a rush because the England game was about to start and that's why I left suddenly.

EDIT: You might also want to get someone to check my answer on this thread, too. Just in case my lack of experience is obvious.

12. Originally Posted by Moo
You can be 22 years old and yet experienced...

But I quite agree that there is no point giving the full solution without any explanation, and it's quite rare that someone more wants the explanations than the solutions ^^
Well I would've thought the intermediate work was obvious for the first 2 when you look at the answers and the questions, but maybe I'm wrong?

For the second question, it alternates between 0 and 2, so it's the modulus of 2 minus the previous value.

0-2 = -2... |-2| = 2

2-2 = 0

13. Originally Posted by robocop_911
I am not getting any serious help here. Where are all the experienced guys? I really need to solve these sums!
I find your comments towards sean offensive, If I was sean I would have stopped offering your help a long time ago. in this thread you are simple just being rude and unappreciative, Sean is offering you very good help and your as opposed to thanking him you're simply being rude, your attitude goes against what a forum like this stands for. I suggest you seek some paid tuition service where "experienced" people will help on demand as with your current attitude I cannot imagine people on this forum will want to help you (myself included).

Bobak

14. Originally Posted by bobak
I find your comments towards sean offensive, If I was sean I would have stopped offering your help a long time ago. in this thread you are simple just being rude and unappreciative, Sean is offering you very good help and your as opposed to thanking him you're simply being rude, your attitude goes against what a forum like this stands for. I suggest you seek some paid tuition service where "experienced" people will help on demand as with your current attitude I cannot imagine people on this forum will want to help you (myself included).
Bobak
Sheesh... cool down...

since this forum is "Urgent" -- I lost my patience...

15. ## Seems like a hard topic

Seems like my topic (questions) is/are really "hard" and odd. No wonder I didn't get any replies up till now!...

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