If the coefficients of x4,x5 and x6 in the expansion of (1 + x)n are in the arithmetic progression. Then the maximum value of n is.
7
28
14
21
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nC4, nC5, nC6 are in A.P.
2 (nC5) = nC4 + nC6 ⇒ n2 – 21n + 98 = 0
(n – 14)(n – 7) = 0 ⇒ n = 7,14
maximum value of n=14