JEE Main & Advanced Mathematics Conic Sections Question Bank Hyperbola

  • question_answer
    The equation of the tangent parallel to \[y-x+5=0\] drawn to \[\frac{{{x}^{2}}}{3}-\frac{{{y}^{2}}}{2}=1\] is   [UPSEAT 2004]

    A)            \[x-y-1=0\]                                

    B)            \[x-y+2=0\]

    C)            \[x+y-1=0\]                               

    D)            \[x+y+2=0\]

    Correct Answer: A

    Solution :

               Given hyperbola is, \[\frac{{{x}^{2}}}{3}-\frac{{{y}^{2}}}{2}=1\]                       .....(i)            Equation of tangent parallel to \[y-x+5=0\] is            \[y-x+\lambda =0\] \[\Rightarrow \]\[y=x-\lambda \]                         .....(ii)            If line (ii) is a tangent to hyperbola (i), then            \[-\lambda =\pm \sqrt{3\times 1-2}\]    (from \[c=\pm \sqrt{{{a}^{2}}{{m}^{2}}-{{b}^{2}}}\])            \[-\lambda =\pm \,1\Rightarrow \lambda =-1,\,+1\].            Put the values of \[\lambda \] in (ii), we get \[x-y-1=0\] and \[x-y+1=0\] are the required tangents.


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