Engineering
Mathematics
Arithmetic Progression and Its Properties
Introduction to Binomial Theorem
Question

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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Solution

 nC4, nC5, nC6 are in A.P.

2 (nC5= nC+ nC6 n– 21+ 98 = 0

(– 14)(– 7) = 0 ⇒ = 7,14

maximum value of n=14