CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2001

  • 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:

    A) \[7/2\]                                 

    B) \[-19\]

    C)  \[-12\]                                

    D)  \[12\]

    Correct Answer: C

    Solution :

    \[12{{x}^{2}}+7xy+a{{y}^{2}}+13x-y+3=0\] \[a=2,\text{ }b=a,\]for perpendiculaty coeff. of                \[{{x}^{2}}+\]coeff. of \[{{y}^{2}}=0\] \[a+b=0\Rightarrow 12+a=0\Rightarrow a=-12\]


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