JEE Main & Advanced Mathematics Conic Sections Question Bank Hyperbola

  • question_answer
    If \[{{m}_{1}}\] and \[{{m}_{2}}\]are the slopes of the tangents to the hyperbola \[\frac{{{x}^{2}}}{25}-\frac{{{y}^{2}}}{16}=1\] which pass through the point (6, 2), then

    A)            \[{{m}_{1}}+{{m}_{2}}=\frac{24}{11}\]                                        

    B)            \[{{m}_{1}}{{m}_{2}}=\frac{20}{11}\]

    C)            \[{{m}_{1}}+{{m}_{2}}=\frac{48}{11}\]                                        

    D)            \[{{m}_{1}}{{m}_{2}}=\frac{11}{20}\]

    Correct Answer: B

    Solution :

     The line through (6,2) is \[y-2=m(x-6)\]Þ\[y=mx+2-6m\] Now from condition of tangency, \[{{(2-6m)}^{2}}=25{{m}^{2}}-16\] Þ\[36{{m}^{2}}+4-24m-25{{m}^{2}}+16=0\] Þ\[11{{m}^{2}}-24m+20=0\] Obviously its roots are \[{{m}_{1}}\]and\[{{m}_{2}}\], therefore \[{{m}_{1}}+{{m}_{2}}=\frac{24}{11}\]and \[{{m}_{1}}{{m}_{2}}=\frac{20}{11}\].


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