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JEE Main & Advanced Mathematics Pair of Straight Lines Question Bank Angle between the pair of straight lines, Condition for parallel and perpendicular lines

  • question_answer
    The equation \[12{{x}^{2}}+7xy+a{{y}^{2}}+13x-y+3=0\] represents a pair of perpendicular lines. Then the value of ?a? is [Karnataka CET 2001]

    A)            \[\frac{7}{2}\]                      

    B)            - 19

    C)            - 12                                           

    D)            12

    Correct Answer: C

    Solution :

               Comparing the given equation with standard equation, we get \[a=12\] and \[b=a\]. We also know that for perpendicular lines, coefficient of \[{{x}^{2}}\]+ coefficient of \[{{y}^{2}}=0\] or \[a+b=0\]. Therefore \[12+a=0\] or \[a=-12\].


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