C4 - Binomial Expansion Q - Help Please - Ignore! Sorry figured it now!!

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  1. rosschambers1987's Avatar
    • Full Member
    • Location: Blackpool
    • Posts: 91
    C4 - Binomial Expansion Q - Help Please - Ignore! Sorry figured it now!!


    I have done the expansion, getting: -

    As you can see, i'm trying to do the last bit, getting 1/0.99 so I can plug in the x value.

    So my question is, how to I represent 1/0.99 in the form

    1 - x/10

    ?

    Or am I barking up the wrong tree? Also, part b asks me to show that the coefficient of x^n is K(n+1)(n+2) * 1/10^n

    I just tried it on x^1 and got 1/2 then plugged this into n=2 to see if it came out right and it did. Was that the correct thing to do?

    Cheers,
    Ross
    Last edited by rosschambers1987; 14-06-2011 at 10:30.
  2. Ch1pp0's Avatar
    • Exalted Member
    • Location: England
    • Posts: 324
    Re: C4 - Binomial Expansion Q - Help Please - Ignore! Sorry figured it now!!
     (\frac {1}{0.99}) ^{-3} = 0.99^3 = (1 - \frac {0.1}{10})^3

    Then you can use your answers from the earlier parts to solve this.
    Hope this helps.
    Last edited by Ch1pp0; 14-06-2011 at 11:55.
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