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anonymous

  • one year ago

MEDAL&FAN&Testimonials (n-r+1)!/(n-r-2)! How do I write this without using factorial notation?

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  1. anonymous
    • one year ago
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    My head's stuck on this problem if anyone could offer me help that would be awesome!

  2. anonymous
    • one year ago
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    @ganeshie8 the almighty?

  3. anonymous
    • one year ago
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    Hi

  4. anonymous
    • one year ago
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    Do you know how to do this problem?

  5. ganeshie8
    • one year ago
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    Hint : let \(n-r+1 = m\)

  6. anonymous
    • one year ago
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    The trickiest part is that denominator is negative whereas the numerator is positive.

  7. anonymous
    • one year ago
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    This makes me feel insecure about canceling either.

  8. anonymous
    • one year ago
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    (m)(m-1)(m-2)/(m-3)(m-4)(m-5)

  9. ganeshie8
    • one year ago
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    \[\dfrac{(n-r+1)!}{(n-r-2)!} = \dfrac{(\color{blue}{n-r+1})!}{(\color{blue}{n-r+1}-3)!} \]

  10. anonymous
    • one year ago
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    Oh!

  11. anonymous
    • one year ago
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    Looks like the factorials are all canceled but (-3)!, at least intuitively.

  12. ganeshie8
    • one year ago
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    Let that blue part equal \(\color{blue}{m}\) : \[\dfrac{(n-r+1)!}{(n-r-2)!} = \dfrac{(\color{blue}{n-r+1})!}{(\color{blue}{n-r+1}-3)!} =\dfrac{\color{blue}{m}!}{(\color{blue}{m}-3)!} =mP3\]

  13. anonymous
    • one year ago
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    1/-3!

  14. anonymous
    • one year ago
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    no no

  15. anonymous
    • one year ago
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    How come mP3 and not 1/-3!?

  16. ganeshie8
    • one year ago
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    recall the definition of permutation : \[nPr = \dfrac{n!}{(n-r)!}\]

  17. anonymous
    • one year ago
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    Oh yes.

  18. anonymous
    • one year ago
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    Not the conventional calculation of fractions.

  19. anonymous
    • one year ago
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    Assuming that rule, (n+4)!/(n+2)! will be not (n+4)(n+3)?

  20. anonymous
    • one year ago
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    (n+4)(n+3)(n+2)(n+1)(n)/(n+2)(n+1)(n)=(n+4)(n+3)? This is not correct?

  21. UsukiDoll
    • one year ago
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    \[\frac{(n+4)(n+3)(n+2)(n+1)(n)}{(n+2)(n+1)(n)}\] cancel like terms should be (n+4)(n+3)

  22. anonymous
    • one year ago
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    At first seemed a bit counterintuitive after what Ganashie showed me.

  23. anonymous
    • one year ago
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    But I guess I am not so retarded at this timeXD

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