JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Expansion of determinants, Solution of equation in the form of determinants and properties of determinants

  • question_answer
    Suppose \[D=\left| \,\begin{matrix}    {{a}_{1}} & {{b}_{1}} & {{c}_{1}}  \\    {{a}_{2}} & {{b}_{2}} & {{c}_{2}}  \\    {{a}_{3}} & {{b}_{3}} & {{c}_{3}}  \\ \end{matrix}\, \right|\]and     \[{D}'=\left| \,\begin{matrix}    {{a}_{1}}+p{{b}_{1}} & {{b}_{1}}+q{{c}_{1}} & {{c}_{1}}+r{{a}_{1}}  \\    {{a}_{2}}+p{{b}_{2}} & {{b}_{2}}+q{{c}_{2}} & {{c}_{2}}+r{{a}_{2}}  \\    {{a}_{3}}+p{{b}_{3}} & {{b}_{3}}+q{{c}_{3}} & {{c}_{3}}+r{{a}_{3}}  \\ \end{matrix}\, \right|\], then [Karnataka CET 1993; Pb. CET 1993]

    A) \[{D}'=D\]

    B) \[{D}'=D(1-pqr)\]

    C) \[{D}'=D(1+p+q+r)\]

    D) \[{D}'=D(1+pqr)\]

    Correct Answer: D

    Solution :

      \[{D}'=D+pqr\,D=D(1+pqr)\]. Trick: Check by putting \[B=I\] and all other zero.


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