Question 891222: I need help with this factorial expression:find the factorial of: 12!/11! 12!/13! Thanks for helping.
Answer by DrBeeee(684)   (Show Source):
You can put this solution on YOUR website! Use the order of evaluation from left to right, we are given
(1) (12!/11!)*(12!/13!)
The first fraction is
(2) 12!/11! = (12*11*10*...)/(11*10*9*...)
Note that the "tail" of the numerator is 11*10*9*..., and is cancelled by the denominator 11*10*9*..., thus reducing (2) to
(3) 12
The second fraction is given by
(4) 12!/13! = (12*11*10*...)/(13*12*11*10*9*...)
For this fraction the "tail" of the denominator is 12*11*10*9*..., and is cancelled by the numerator 12*11*10*9*..., thus reducing (4) to
(5) 1/13
Then we have (1) reducing to
(6) 12/13
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