Medium MCQ +4 / -1 PYQ · JEE Mains 2022

Let A and B be two $3 \times 3$ non-zero real matrices such that AB is a zero matrix. Then

  1. A the system of linear equations $A X=0$ has a unique solution
  2. B the system of linear equations $A X=0$ has infinitely many solutions Correct answer
  3. C B is an invertible matrix
  4. D $\operatorname{adj}(\mathrm{A})$ is an invertible matrix

Solution

<p>AB is zero matrix</p> <p>$\Rightarrow |A| = |B| = 0$</p> <p>So neither A nor B is invertible</p> <p>If $|A| = 0$</p> <p>$\Rightarrow |\mathrm{adj}\,A| = 0$ so $\mathrm{adj}\,A$</p> <p>$AX = 0$ is homogeneous system and $|A| = 0$</p> <p>So, it is having infinitely many solutions</p>

About this question

Subject: Mathematics · Chapter: Matrices and Determinants · Topic: Types of Matrices and Operations

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