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    https://b940eb267c31463d4d23ccfd3105...%20Edexcel.pdf

    help with 3a with the 3rd term in the expansion please.

    so far i have 1.\left(\dfrac{x}{4}\right)

    not sure about the power which goes on the x/4 and how to express ^n\mathrm{C}_2 as a coefficient
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    (Original post by thefatone)
    https://b940eb267c31463d4d23ccfd3105...%20Edexcel.pdf

    help with 3a with the 3rd term in the expansion please.

    so far i have 1.\left(\dfrac{x}{4}\right)

    not sure about the power which goes on the x/4 and how to express ^n\mathrm{C}_2 as a coefficient
    I recommend you use the formula given in the Edexcel formula book for:

    \displaystyle (1+x)^n
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    (Original post by notnek)
    I recommend you use the formula given in the Edexcel formula book for:

    \displaystyle (1+x)^n
    i see... are you supposed to learn about that or is it just given and you know how to use it?
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    (Original post by thefatone)
    i see... are you supposed to learn about that or is it just given and you know how to use it?
    Both?
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    (Original post by Zacken)
    Both?
    ... so how would you get the 3rd term of the expansion of \left(1+x\right)^n

    i'm not sure about this i haven't been taught this :/
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    (Original post by thefatone)
    ... so how would you get the 3rd term of the expansion of \left(1+x\right)^n

    i'm not sure about this i haven't been taught this :/
    It's given in the booklet, it's \frac{n(n-1)(n-2)}{3!} x^3
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    (Original post by Zacken)
    It's given in the booklet, it's \frac{n(n-1)(n-2)}{3!} x^3
    would i ever need to "show" that ?
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    (Original post by thefatone)
    would i ever need to "show" that ?
    No.But it's not hard: \displaystyle ^n\mathrm{C}_3 = \frac{n!}{(n-3)! 3!} = \frac{n(n-1)(n-2)(n-3)!}{(n-3)! 3!} = \frac{n(n-1)(n-2)}{3!}
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    (Original post by thefatone)
    https://b940eb267c31463d4d23ccfd3105...%20Edexcel.pdf

    help with 3a with the 3rd term in the expansion please.

    so far i have 1.\left(\dfrac{x}{4}\right)

    not sure about the power which goes on the x/4 and how to express ^n\mathrm{C}_2 as a coefficient
    if you did c4 this question would have made more sense, binomial questions to the power of N has never come up on edexcel papers. But as stated below you would need to do the long method of working it out
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    (Original post by thefatone)
    https://b940eb267c31463d4d23ccfd3105...%20Edexcel.pdf

    help with 3a with the 3rd term in the expansion please.

    so far i have 1.\left(\dfrac{x}{4}\right)

    not sure about the power which goes on the x/4 and how to express ^n\mathrm{C}_2 as a coefficient
    finding and simplifying in part a should still be in terms of n, then for part be you can use that to answer
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    (Original post by Zacken)
    No.But it's not hard: \displaystyle ^n\mathrm{C}_3 = \frac{n!}{(n-3)! 3!} = \frac{n(n-1)(n-2)(n-3)!}{(n-3)! 3!} = \frac{n(n-1)(n-2)}{3!}
    I see thanks a ton
    wait when does n factorial expand to all those brackets????
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    (Original post by thefatone)
    I see thanks a ton
    wait when does n factorial expand to all those brackets????
    What does the factorial represent?

    \displaystyle 

\begin{equation*}n! = n\underbrace{(n-1)(n-2)(n-3)\cdots (2)(1)}_{(n-1)!}\end{equation*}

    Or

    \displaystyle 

\begin{equation*} n!=n(n-1)\underbrace{(n-2)\cdots (2)(1)}_{(n-2)!} = n(n-1)(n-2)! \end{equation*}

    Or...

    It's not hard if you just think for a bit.
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    (Original post by thefatone)
    I see thanks a ton
    wait when does n factorial expand to all those brackets????
    imagine 5! ... 5x4x3 etc... minusing 1 each time
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    (Original post by Zacken)
    What does the factorial represent?

    \displaystyle 

\begin{equation*}n! = n\underbrace{(n-1)(n-2)(n-3)\cdots (2)(1)}_{(n-1)!}\end{equation*}

    Or

    \displaystyle 

\begin{equation*} n!=n(n-1)\underbrace{(n-2)\cdots (2)(1)}_{(n-2)!} = n(n-1)(n-2)! \end{equation*}

    Or...

    It's not hard if you just think for a bit.
    thanks
 
 
 
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