Mark the correct alternative in the following : If the coefficients of 2 nd , 3 rd and 4 th terms in the expansion of are in A.P., then n =

Question

Philoid · Accepted Answer

Given:

T₂; T₃& T₄

Since T₂ , T₃ & T₄ are in AP

Then; 2(T₃) = T₂ + T₄

i.e.

(n-1)(n-2)-6(n-1)+6=0

n²-3n+2-6n+6+6=0

n²-9n+14=0

(n-2)(n-7)=0

n= 2,7

n=2 rejected for term 3^rd

So n=7