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Math Help - "Recursive definition"

  1. #1
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    Post "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!
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  2. #2
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    Quote Originally Posted by robocop_911 View Post
    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
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  3. #3
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    b) a1 = 0 an = |an-1 - 2|
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    Quote Originally Posted by sean.1986 View Post
    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.
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  5. #5
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by robocop_911 View Post
    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
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  6. #6
    Moo
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    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
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    Quote Originally Posted by Mathstud28 View Post
    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?
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  8. #8
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by robocop_911 View Post
    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
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  9. #9
    Moo
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    Quote Originally Posted by robocop_911 View Post
    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 ^^
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  10. #10
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    Quote Originally Posted by Moo View Post
    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!
    Last edited by robocop_911; June 1st 2008 at 03:29 PM.
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  11. #11
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    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.
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  12. #12
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    Quote Originally Posted by Moo View Post
    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
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  13. #13
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    Quote Originally Posted by robocop_911 View Post
    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
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  14. #14
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    Quote Originally Posted by bobak View Post
    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...
    Last edited by robocop_911; June 1st 2008 at 04:44 PM.
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  15. #15
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    Thumbs down 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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