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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