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What is meant by U_n

  1. Jun 8, 2012 #1
    161i8a0.png

    Could anyone explain what is meant by [tex] U_n [/tex]
     
  2. jcsd
  3. Jun 8, 2012 #2

    micromass

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    It are just numbers. That is, [itex]U_1,...,U_n[/itex] are just numbers. You need to figure out which numbers they are.
     
  4. Jun 8, 2012 #3
    Hi synkk
    The wording is probably confusing you.
    First, did you do (a) ? do it if you didn't

    Then, as micromass told you, Un is just a number, well, in this case, you are dealing with a sequence of numbers, U1, ... Un
    You have a generic formula for their sum, which is a function of n, being the result of summing the n elements U1,...Un
    so, if you subtract the sum of all the elements, U1,...Un-1, what are you left with ?
    Hope this helps so that you continue alone

    Cheers...
     
  5. Jun 8, 2012 #4

    HallsofIvy

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    Another way of looking at (a): if you were told that f(n)= n^2+ 4n, how would you find f(n-1)?

    Then (b), what is f(n)- f(n-1)?
     
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