Let denote the sum of the first terms of an arithmetic progression (A.P.) whose first term is and the common difference is . Let
is always
is always
- (A)an odd number
- (B)an even number
- (C)a prime number
- (D)a composite number✓ Correct
Answer: (D)
Solution
From the previous calculation:
Therefore,
Factoring:
Since is a product of two factors both greater than 1 for , it is always a composite number.
Therefore,
Factoring:
Since is a product of two factors both greater than 1 for , it is always a composite number.
JEE Advanced · 2007 · 08 Apr 2007 · Paper 1 · Single correct option