JEE Main 2017MathematicsMatricesHardMCQ

JEE Main 2017 — Matrices Question with Solution

JEE Main 2017 (08 Apr Online)

Question

Let A be any 3×3 invertible matrix. Then which one of the following is not always true?

Choose an option

Show full solutionCorrect option: B
Correct answer
Badj adj (A)=A.adj (A)-1

Step-by-step explanation

∵A-1=1AadjA

∴adjadjA=adj Aadj A-1=A2adj A-1……i

∵Aadj A=AI

∴adjA=AA-1

∴adj A-1=1AA

∴  from (i) 

adjadj A=A.A

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About this question

This is a previous-year question from JEE Main 2017, covering the Matrices 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.