math

n!/(n-2)!=90

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asked by mr
  1. n=10

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    posted by Jen
  2. how did u get the n=10

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    posted by mr
  3. rewrite it as ...
    n!/(n-2)!=90
    [n(n-1)(n-2)(n-3)..(2)(1)]/(n-2)(n-3)..(2)(1)] = 90

    n(n-1) = 90
    n^2 - n = 90 = 0
    (n-10)(n+9)=0
    n=10 or n= -9 , but n > 0

    so n=10

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    posted by Reiny

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