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

  • question_answer
    The equation of the lines passing through the origin and having slopes 3 and \[-\frac{1}{3}\] is

    A)            \[3{{y}^{2}}+8xy-3{{x}^{2}}=0\]                                       

    B)            \[3{{x}^{2}}+8xy-3{{y}^{2}}=0\]

    C)            \[3{{y}^{2}}-8xy+3{{x}^{2}}=0\]                                       

    D)            \[3{{x}^{2}}+8xy+3{{y}^{2}}=0\]

    Correct Answer: B

    Solution :

               \[{{m}_{1}}=3,\ \ {{m}_{2}}=-\frac{1}{3}\]. Hence, the lines are\[y=3x,\ y=-\frac{1}{3}x\].                    Multiplying both the lines, we get                    \[(y-3x)(3y+x)=0\Rightarrow 3{{x}^{2}}+8xy-3{{y}^{2}}=0.\]


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