Question
Mathematics Question on Binomial theorem
If the coefficients of 5th, 6th and 7th terms in the expansion of (1+x)n are in A.P. then n =
A
7
B
14
C
7 or 14
D
8
Answer
7 or 14
Explanation
Solution
n2−(4r+1)n+4r2−2=0 where r = 5
If the coefficients of 5th, 6th and 7th terms in the expansion of (1+x)n are in A.P. then n =
7
14
7 or 14
8
7 or 14
n2−(4r+1)n+4r2−2=0 where r = 5