find r!(24-r)!/((r+2)!(24-r-2)!)

👨🏻‍🏫 學術台數學

2008-06-20 1:13 am

點解r!(24-r)!/((r+2)!(24-r-2)!)

= (24-r)(24-r-1)/((r+1)(r+2))

5明呢步

回答 (2)

2008-06-20 2:57 am

✔ 最佳答案

AS follow AS~

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2008-06-20 1:22 am

r!(24-r)!/((r+2)!(24-r-2)!)
=r!(24-r)(24-r-1)(24-r-2)/(r+2)(r+1)(r)!(24-r-2)
=(24-r)(24-r-1)/(r+1)(r+2)

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