12th Class Mathematics Determinants Question Bank Assertion And Reason (MCQs) - Determinants

  • question_answer
    Assertion : If \[{{\left| A \right|}^{2}}=25\] then \[\left| A \right|=\pm \frac{1}{5}\]
    Reason: \[\left| AB \right|=\left| A \right|\,\,\,\left| B \right|\]

    A) Both A and R are individually true and R is the correct explanation of A.

    B) Both A and R are individually true and R is not the correct explanation of A.

    C) 'A' is true but 'R' is false

    D) 'A' is false but 'R' is true

    E) Both A and R are false.

    Correct Answer: D

    Solution :

    Given Assertion is \[\left| {{A}^{2}} \right|=25\Rightarrow \,\,\left| AA \right|=25\] \[\Rightarrow \,\,\,\left| A \right|\,\,\left| A \right|=25\,\,\Rightarrow \,{{\left| A \right|}^{2}}=25\,\,\Rightarrow \left| A \right|=\pm \,5\] \[\therefore \]Given Assertion [A] is false Also \[\left| AB \right|=\left| A \right|\,\,\,\left| B \right|\]{property of determinant}, \[\therefore \]Reason (R) is true. Hence option [D] is the correct answer.


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