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: Combinations Problem

  1. May 20, 2008 #1
    1. The problem statement, all variables and given/known data
    http://img234.imageshack.us/img234/8519/combgf7.png [Broken]​

    2. Relevant equations

    3. The attempt at a solution
    The picture I have shown contains the problem and the teacher's solution. However, I was wondering how the [tex]k[/tex] value is 3. And no, I can't ask the teacher; my test is tomorrow.
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. May 20, 2008 #2


    User Avatar
    Homework Helper

    This is how I would do it



    and you want the coefficient of [itex]x^11[/itex]

    so if you expand you will get


    You need to find k and you want the power of x to be 11

    so that 3k-10=11

    See it?
  4. May 20, 2008 #3
    For your expansion, isn't the 1 supposed to be where the [tex]x^3[/tex] is? Because 1 is the y value, while [tex]x^3[/tex] is the x value.

    Also, k doesn't equal 3 in [tex]3k-10=11[/tex]
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook