JEE Main 2019 — Sequences And Series Question with Solution
From: JEE Main 2019 (Online) 9th January Evening Slot
Question
Let a, b and c be the 7th, 11th and 13th terms respectively of a non-constant A.P. If these are also three consecutive terms of a G.P., then equal to :
Choose an option
Show full solutionCorrect option: D
Correct answer
D4
Step-by-step explanation
T7 = A + 6d = a; T11 = A + 10d = b; T13 = A + 12d = c
Now a, b, c are in G.P.
b2 = ac
(A + 10d)2 = (A + 6d) (A + 12d)
A2 + 100d2 + 20Ad = A2 + 18Ad + 72d2
A + 14d = 0, A = 14d
Now a, b, c are in G.P.
b2 = ac
(A + 10d)2 = (A + 6d) (A + 12d)
A2 + 100d2 + 20Ad = A2 + 18Ad + 72d2
A + 14d = 0, A = 14d
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This is a previous-year question from JEE Main 2019, covering the Sequences And Series chapter of Mathematics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.