1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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
    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

    User Avatar
    Science Advisor

    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)?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook