JEE Main & Advanced Mathematics Pair of Straight Lines Question Bank Equation of Pair of Straight Lines

  • question_answer
    The equation of lines passing through the origin and parallel to the lines \[y={{m}_{1}}x+{{c}_{1}}\] and \[y={{m}_{2}}x+{{c}_{2}}\] is

    A)            \[{{m}_{1}}{{m}_{2}}{{x}^{2}}-({{m}_{1}}+{{m}_{2}})xy+{{y}^{2}}=0\]

    B)            \[{{m}_{1}}{{m}_{2}}{{x}^{2}}+({{m}_{1}}+{{m}_{2}})xy+{{y}^{2}}=0\]

    C)            \[{{m}_{1}}{{m}_{2}}{{y}^{2}}-({{m}_{1}}+{{m}_{2}})xy+{{x}^{2}}=0\]

    D)            \[{{m}_{1}}{{m}_{2}}{{y}^{2}}+({{m}_{1}}+{{m}_{2}})xy+{{x}^{2}}=0\]

    Correct Answer: A

    Solution :

               Passing through origin and is parallel to given lines are \[y={{m}_{1}}x\]and\[y={{m}_{2}}x\]. If represented as pair of straight lines, we get \[(y-{{m}_{1}}x)(y-{{m}_{2}}x)=0\]                    \[\Rightarrow {{m}_{1}}{{m}_{2}}{{x}^{2}}-({{m}_{1}}+{{m}_{2}})xy+{{y}^{2}}=0\].


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