Sequence And Series Question 508
Question: If $ S_{n}=nP+\frac{1}{2}n(n-1)Q $ , where $ S_{n} $ denotes the sum of the first $ n $ terms of an A.P., then the common difference is
[WB JEE 1994]
Options:
A) $ P+Q $
B) $ 2P+3Q $
C) $ 2Q $
D) $ Q $
Show Answer
Answer:
Correct Answer: D
Solution:
Obviously $ S_{n}=\frac{n}{2}{2P+(n-1)Q} $ , hence $ d=Q $ . Aliter: $ d=T_2-T_1 $ $ =(S_2-S_1)-S_1 $ $ =S_2-2S_1=2P+Q-2P=Q. $
BETA
