Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Hi all PLEASE HELP

  1. May 26, 2009 #1
    Hi All,

    I am having trouble solving an equation for X because the equation has summations of the X value to a power. Can anybody help me find the best way to solve this type of equation. I have included a simple example of what I mean below:

    20
    E {const/[(1+X)^t]} = const
    t=4

    Do you know if this can be simplified or if you can get the x on its own?

    Thanks a million for any help with this..

    Regards,

    Gary
     
  2. jcsd
  3. May 26, 2009 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    [tex]\sum_{t=4}^{20} \frac{C}{(1+x)^t}= C[/tex]
    Is that your equation? You can factor that "C" out and cancel:
    [tex]\sum_{t=4}^{20}\frac{1}{(1+x)^t}= 1[/tex]

    That's a "geometric series". The geometric series [tex]\sum_{t=0}^n r^t= \frac{1- r^{n+1}}{1- r}[/tex] as long as |r|< 1. Here r= 1/(1+x). Also since your sum starts at 4 rather than 0, you should use that formula with n= 20 and 3 and subtract to get a "closed form" equation.
     
  4. May 26, 2009 #3
    Hi,

    Thanks for your reply but I had the equation in wrong. I tried to simplify the equation I am working with in order to post it. This is closer to what I need, I can get values for everything except Z and I was wondering if it was possible to get the equation in the form of Z = ...........
    4 20
    V = E {(Xt.Yt)/[(1+Z+3%)^t]} + E {X4.Y4.(D)/[(1+Z+3%)^t]} + .....
    t=0 t=4


    ...... [1/(1+Z+3%)^t].(X20.Yo/z+3%-I)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Hi all PLEASE HELP
Loading...