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f four times the number of permutations ...

f four times the number of permutations of n things 3 togetherisecuar to five times the number of permutations ofn -1 things 3 together, find

Text Solution

Verified by Experts

Given
` 4xx (n_(P_3))​=5xx((n−1)_(P_3))​`
=`4xx(n!​)/((n−3)!)=5xx((n−4)!)/((n−1)!)`
​ =`4xxn=5xx(n−3)`
=`4n=5n−15 ...
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