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Math Help - Permutation.......

  1. #1
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    Permutation.......

    Hi all, need some help here,

    Simplify

    2n+2
    . .Pn
    2n
    . .Pn


    thanks
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  2. #2
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    Quote Originally Posted by micmac63 View Post
    Hi all, need some help here,

    Simplify

    2n+2
    . .Pn
    2n
    . .Pn


    thanks
    Simplify \frac{^{2n+2}P_n}{^{2n}P_n}.

    Do you know that ^n P_r = \frac{n!}{(n-r)!} ?
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  3. #3
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    yes, but dont quite understand ?????
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  4. #4
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    Quote Originally Posted by mr fantastic View Post
    Simplify \frac{^{2n+2}P_n}{^{2n}P_n}.

    Do you know that ^n P_r = \frac{n!}{(n-r)!} ?
    Quote Originally Posted by micmac63 View Post
    yes, but dont quite understand ?????
    \frac{^{2n+2}P_n}{^{2n}P_n} = \frac{\frac{(2n+2)!}{(2n+2-n)!}}{\frac{(2n)!}{(2n-n)!}} = \frac{\frac{(2n+2)!}{(n+2)!}}{\frac{(2n)!}{n!}} = \frac{(2n+2)!}{(n+2)!} \times \frac{n!}{(2n)!} = .....
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  5. #5
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    Thankyou so much, Im helping my daughter with this, and she is on right track now,

    if the equation equals 3.5, find the value of n ?





    thanks again.
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  6. #6
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    Quote Originally Posted by micmac63 View Post
    Thankyou so much, Im helping my daughter with this, and she is on right track now,

    if the equation equals 3.5, find the value of n ?





    thanks again.
    Solve \frac{(2n+2)(2n+1)}{(n+2)(n+1)} = \frac{7}{2} \Rightarrow 2(2n+2)(2n+1)=7(n+2)(n+1) .....

    Expand both sides and re-arrange into the form:

    quadratic = 0.

    Solve this equation in the usual way, noting the restriction n \geq 0.

    For checking purposes: n = 10.
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