JEE Main 2021MathematicsSequences and SeriesEasyNumerical

JEE Main 2021 — Sequences and Series Question with Solution

JEE Main 2021 (16 Mar Shift 2)

Question

Let 116,a and b be in G.P. and 1a,1 b,6 be in A.P., where a,b>0. Then 72(a+b) is equal to _______ .

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Show full solutionCorrect answer: 14
Correct answer
14

Step-by-step explanation

a2=b16⇒1b=116a2

2b=1a+6

18a2=1a+6

1a2-8a-48=0

1a=12,-4⇒a=112,-14

a=112,a>0

b=16a2=19

⇒72(a+b)=6+8=14

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About this question

This is a previous-year question from JEE Main 2021, 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.