First slide
Binomial theorem for positive integral Index
Question

If the sum of the coefficients in the expansion of (a + b)n is 4096, then the greatest coefficient in the expansion is

Easy
Solution

We know that the sum of the coefficients in a binomial expansion is obtained by replacing each variable by ‘1’ in the given expression. Therefore, sum of the coefficients in (a + b)n is given by (1 + 1)n.

 4096=2n

or 2n=212  or n=12

Hence, n is even. So, the greatest coefficient is  nCn/2, i.e., 12C6=924.

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