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

  • question_answer
    Assertion: \[\left| P \right|=O\]
    Reason : Determinant of skew symmetric matrix is O.

    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: C

    Solution :

    Given Assertion is \[\left| P \right|=O\Rightarrow \left| P' \right|=O\]
    \[\left( \because \,\,\left| A \right|=\left| A' \right| \right)\]
    Also for skew symmetric matrix \[A'=-A\]
    \[\therefore \,\,\,\left| A' \right|=\det \left( -A \right)={{\left( -1 \right)}^{n}}\,\det \,\,A\]
    If n is even, then \[\left| A' \right|=\left| A \right|\]
    If n is odd, then \[\left| A' \right|=-\left| A \right|\]
    \[\Rightarrow \,\,\left| A \right|=-\left| A \right|\Rightarrow 2\left| A \right|=0\Rightarrow \left| A \right|=0\]
    \[\therefore \,\,\,\left| A \right|=0\]is possible when n is odd
    \[\therefore \]Given Reason (R) is not valid for Assertion [A]
    \[\therefore \]Assertion is true but Reason is false
    Hence option [C] is the correct answer.


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