JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2008

  • question_answer
        The lines represented by\[a{{x}^{2}}+2gxy+b{{y}^{2}}=0\] 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\[\theta =90{}^\circ \] \[\Rightarrow \]               \[\tan \theta =\frac{2\sqrt{{{h}^{2}}-ab}}{a+b}\] \[\Rightarrow \]               \[\tan 90{}^\circ =\frac{2\sqrt{{{h}^{2}}-ab}}{a+b}\] \[\Rightarrow \]               \[\frac{1}{0}=\frac{2\sqrt{{{h}^{2}}-ab}}{a+b}\] \[\Rightarrow \]               \[a+b=0\]


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