Q. 164.0( 3 Votes )

If the seventh term from the beginning and end in the binomial expansion of are equal, find n.

Answer :

In the binomial expansion of


[(n + 1)-7 + 1]th


i.e. (n - 5)th term from the beginning is a 7th term from the end.


Now, T7 = T6 + 1


T6 + 1 = nC6


= nC6


And, Tn - 5 = Tn - 5 - 1


Tn - 6 = nCn - 6 = nC6


It is given that,


T7=Tn - 5


nC6 = nC6




On equating the exponent



n = 12


Hence, the value of n is 12


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