Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • Engineering
  • Let Sn denote the sum of the first n terms of an A.P, a1, a2, a3,......an. If a5 + a9 = 1 and S9 = 6, then which of the

Let Sn denote the sum of the first n terms of an A.P, a1, a2, a3,......an. If a5 + a9 = 1 and S9 = 6, then which of the following is not true?

Option: 1

a13 = 0


Option: 2

S13 = 13/2


Option: 3

s6 = - 19/4


Option: 4

a6 + a8 = 1


Answers (1)

best_answer

Sum of n terms of an AP -

\begin{array}{l}{S_{n}=\frac{n}{2}[2 a+(n-1) d]} \\ {\text { OR }} \\ {S_{n}=\frac{n}{2}[a+l]} \\ {a \rightarrow \text { first term }} \\ {d \rightarrow \text { common difference }} \\ {n \rightarrow \text { number of terms }}\end{array}

 

Given,

S6 = 3 ( 2 + 5(-1/12)) = -19/4

Posted by

vinayak

View full answer

JEE Main high-scoring chapters and topics

Study 40% syllabus and score up to 100% marks in JEE

Similar Questions

Trending Articles/News

anam-khan

JEE Main 2026 session 2 application correction begins on jeemain.nta.nic.in; edit details by tomorrow
anam-khan

JEE Main 2026 Registration LIVE: Session 2 exam from April 2 to 9; shift timings, admit card, exam pattern
anam-khan

JEE Main 2026 session 2 registration ends today for BTech, BArch; apply at jeemain.nta.nic.in

Latest Question