Sunday, December 14, 2008

To find the greatest term in the expansion of (x+a)n

(i) Write (r+1)th term = T(r+1) and rth term = T (r)from the given expression.
(ii) Find T(r+1)/T(r)
(iii) Put T(r+1)/T(r)>1
(iv) Solve the inequality for r to get an inequality of the form rm

If m is an integer, the mth and (m+1)th terms are equal in magnitude and these two are the greatest terms.

If m is not an integer, then obtain integral part of m, say, k. In this case (k+1) term is the greatest term

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