JEE Main & Advanced Mathematics Straight Line Question Bank Problems related to triangle and quadrilateral Locus

  • question_answer
    The area of a parallelogram formed by the lines \[ax\pm by\pm c=0\], is                                         [IIT 1973]

    A)            \[\frac{{{c}^{2}}}{ab}\]             

    B)            \[\frac{2{{c}^{2}}}{ab}\]

    C)            \[\frac{{{c}^{2}}}{2ab}\]           

    D)            None of these

    Correct Answer: B

    Solution :

               \[ax\pm by\pm c=0\Rightarrow \frac{x}{\pm c/a}+\frac{y}{\pm c/b}=1\] which meets on axes at \[A\text{ }\left( \frac{c}{a},0 \right)\text{ },\text{  }\]\[C\text{ }\left( -\frac{c}{a},0 \right)\text{ },\text{ }\]\[\text{ }B\text{  }\left( 0,\frac{c}{b} \right)\], \[D\text{ }\left( 0,-\frac{c}{b} \right)\].                    Therefore, the diagonals AC and BD of quadrilateral ABCD are perpendicular, hence it is a rhombus whose area is given by \[=\frac{1}{2}AC\times BD=\frac{1}{2}\times \frac{2c}{a}\times \frac{2c}{b}=\frac{2{{c}^{2}}}{ab}\].


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