Results 1 to 5 of 5

Math Help - Summation Problem

  1. #1
    Newbie
    Joined
    Apr 2009
    Posts
    6

    Summation Problem

    Hi all,
    I have a homework assignment from my calc. 2 class and one of the problems is really difficult for me. I am supposed to come up with a general formula for the summation from k = m to n of [(-1)^k^2][x^2k].
    I don't want the answer, but I don't know where to begin.
    I'm pretty sure I have to manipulate it into a simple geometric sum with only k as an exponent, but the algebra is working up my nerves.

    Thanks in advance for the help
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    Apr 2009
    Posts
    6
    Also, is there a general rule or method for handling summations involving multiplication?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Behold, the power of SARDINES!
    TheEmptySet's Avatar
    Joined
    Feb 2008
    From
    Yuma, AZ, USA
    Posts
    3,764
    Thanks
    78
    Quote Originally Posted by swashbucklord View Post
    Hi all,
    I have a homework assignment from my calc. 2 class and one of the problems is really difficult for me. I am supposed to come up with a general formula for the summation from k = m to n of [(-1)^k^2][x^2k].
    I don't want the answer, but I don't know where to begin.
    I'm pretty sure I have to manipulate it into a simple geometric sum with only k as an exponent, but the algebra is working up my nerves.

    Thanks in advance for the help
    Here is a hint

    a^{2k}=(a^2)^k

    and (-1)^{k^2}=1 for k even

    (-1)^{k^2}=-1 for k odd

    I hope this helps
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Apr 2009
    Posts
    6
    thanks a lot, I ended up with

    ((-x^2) - (-x^2)^(n + 1))/(1 - (-x^2)) - ((-x^2) - (-x^2)^(m - 1))/(
    1 - (-x^2))

    I hope thats right

    P.S. what program or application do you need to be able to write in mathematical equations or symbols?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Apr 2009
    Posts
    6
    I just realized a much simpler method and got the answer

    ((-x^2)^m - (-x^2)^(n + 1))/(1 - (-x^2))

    which is equivalent to my previous answer

    thanks again
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Summation Problem
    Posted in the Discrete Math Forum
    Replies: 2
    Last Post: December 29th 2010, 03:23 PM
  2. summation problem.
    Posted in the LaTeX Help Forum
    Replies: 3
    Last Post: October 4th 2010, 03:14 AM
  3. Summation problem
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: December 2nd 2009, 04:50 PM
  4. summation problem
    Posted in the Pre-Calculus Forum
    Replies: 22
    Last Post: November 7th 2009, 11:09 PM
  5. Summation problem
    Posted in the Algebra Forum
    Replies: 5
    Last Post: August 27th 2007, 11:21 AM

Search Tags


/mathhelpforum @mathhelpforum