MCQ
Let $A$ and $B$ be two $3 \times 3$ non-zero real matrices such that $AB$ is a zero matrix. Then.
  • A
    The system of linear equations $AX =0$ has a unique solution
  • The system of linear equations $AX =0$ has infinitely many solutions
  • C
    $B$ is an invertible matrix
  • D
    $\operatorname{adj}$ $(A)$ is an invertible matrix

Answer

Correct option: B.
The system of linear equations $AX =0$ has infinitely many solutions
b
$AB =0 \Rightarrow| AB |=0$

If $| A | \neq 0, B =0$ (not possible)

If $| B | \neq 0, A =0$ (not possible)

Hence $| A |=| B |=0$

$AX =0$ has infinitely many solutions

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