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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