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Math Help - Factorial Notation.

  1. #1
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    Factorial Notation.

    How would I solve this question?

    Simplify, neW

    n(n-1)! the answer is suppose to be n!

    and

    (n-1)!(n^2+n) the answer is suppose to be (n+1)!
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  2. #2
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    n(n-1)! = n[(n-1)(n-2)(n-3)...(3)(2)(1)] = n(n-1)(n-2)(n-3)...(3)(2)(1) = ?
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  3. #3
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    (n-1)!(n^2+n) = (n-1)!n^2+n(n-1)! = n*n!+n!=n!(n+1) = (n+1)!
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  4. #4
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    Can you help me with this one

    Solve for n.

    P(n,1)=6
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  5. #5
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    Quote Originally Posted by Skoz View Post
    Simplify, neW
    n(n-1)! the answer is suppose to be n!
    and
    (n-1)!(n^2+n) the answer is suppose to be (n+1)!
    You are missing out on some part of the definition.
    \begin{gathered}  n(n - 1)! = n! \hfill \\  10\left( {9!} \right) = 10! \hfill \\ \end{gathered}
    Thus, (n - 1)!\left[ {n^2  + n} \right] = (n - 1)!\left[ {n\left( {n + 1} \right)} \right] = \left[ {n(n - 1)!} \right](n + 1) = \left[ {n!} \right](n + 1) = (n + 1)!
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  6. #6
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    Quote Originally Posted by Skoz View Post
    Can you help me with this one

    Solve for n.

    P(n,1)=6
    Step 1: \frac{n!}{(n-1)!} = 6
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  7. #7
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    Can someone tell me how I can approach this problem because im not sure if its a formula based question, the answer is suppose to be 5/17.

    A bag contains 10 red jellybeans and 8 black jellybeans.

    What is the probability that 2 jellybeans selected at random are red?
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  8. #8
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    Quote Originally Posted by Skoz View Post
    Can someone tell me how I can approach this problem because im not sure if its a formula based question, the answer is suppose to be 5/17.

    A bag contains 10 red jellybeans and 8 black jellybeans.

    What is the probability that 2 jellybeans selected at random are red?
    Questions unrelated to a thread need to be asked in a new thread. Otherwise threads get too confusing and messy.

    For this question I'd suggest drawing a tree diagram. Then it's esay to see that Pr(RR) = (10/18) (9/17) = 10/34 = 5/17.
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