The coefficients of the (r-1)^ th , r^ th and (r+1)^ th terms in the expansion of (1+x)^n are in the ratio...

Question

The coefficients of the (r-1)^ th , r^ th and (r+1)^ th terms in the expansion of (1+x)^n are in the ratio 1:3:5. Find the average of the coefficients of the (r-1)^ th , r^ th and (r+1)^ th terms.

Accepted Answer

21

JEE Main Mathematics question

Solution

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