CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2006

  • question_answer
    The lines represented by \[a{{x}^{2}}+2hxy+b{{y}^{2}}=0\] are perpendicular to each other, if:

    A)  \[{{h}^{2}}=a+b\]           

    B)  \[a+b=0\]

    C)  \[{{h}^{2}}=ab\]                             

    D)  \[h=0\]

    Correct Answer: B

    Solution :

    We know, if the lines are perpendicular to each other, then \[\theta ={{90}^{o}}\] \[\Rightarrow \]               \[\tan \theta =\frac{2\sqrt{{{h}^{2}}-ab}}{a+b}\] \[\Rightarrow \]               \[\tan {{90}^{o}}=\frac{2\sqrt{{{h}^{2}}-ab}}{a+b}\] \[\Rightarrow \]               \[\frac{1}{0}=\frac{2\sqrt{{{h}^{2}}-ab}}{a+b}\] \[\Rightarrow \]               \[a+b=0\]


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