Q10. The coefficients of the th , rth and th terms in the expansion of are in the ratio 1 : 3 : 5. Find n and r.
As we know that the general term in the binomial expansion of is given by
So,
Term in the expansion of :
Term in the expansion of :
Term in the expansion of :
Now, As given in the question,
From here, we get ,
Which can be written as
From these equations we get,