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Math Help - Functions

  1. #1
    Member rtblue's Avatar
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    Functions

    Given: f(x)=2x+f(x-1)  and  f(1)=4, find f(9) (sorry guys, latex is being uncooperative. towards the end that says: and f(1)=4, find f(9).)

    Could anyone suggest where i might begin this problem?
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  2. #2
    Behold, the power of SARDINES!
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    Quote Originally Posted by rtblue View Post
    Given: f(x)=2x+f(x-1)  and  f(1)=4, find f(9) (sorry guys, latex is being uncooperative. towards the end that says: and f(1)=4, find f(9).)

    Could anyone suggest where i might begin this problem?
    The function is define recursively

    Notice that

    f(2)=2(2)+f(2-1)=4+f(1)=4+4=8 and now

    f(3)=2(3)+f(2)=6+8=...
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  3. #3
    MHF Contributor

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    Or, work backwards:
    f(9)= 2(9)+ f(8)= 18+ (2(8)+ f(7))= 18+ 16+ (2(7)+ f(6)), etc.

    (It's generally not a good idea to put text into LaTex. If you didn't mean to then you probably missed the [/ math] at the end.)
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