JCECE Engineering JCECE Engineering Solved Paper-2006

  • question_answer
    The equation of the chord joining two points \[({{x}_{1}},\,\,{{y}_{1}})\] and \[({{x}_{2}},\,\,{{y}_{2}})\] on the rectangular hyperbola \[xy={{c}^{2}}\] is:

    A) \[\frac{x}{{{x}_{1}}+{{x}_{2}}}+\frac{y}{{{y}_{1}}+{{y}_{2}}}=1\]

    B) \[\frac{x}{{{x}_{1}}-{{x}_{2}}}+\frac{y}{{{y}_{1}}-{{y}_{2}}}=1\]

    C) \[\frac{x}{{{y}_{1}}+{{y}_{2}}}+\frac{y}{{{x}_{1}}+{{x}_{2}}}=1\]

    D) \[\frac{x}{{{y}_{1}}-{{y}_{2}}}+\frac{y}{{{x}_{1}}-{{x}_{2}}}=1\]

    Correct Answer: C

    Solution :

    The mid-point of the chord is\[\left( \frac{{{x}_{1}}+{{x}_{2}}}{2},\,\,\frac{{{y}_{1}}+{{y}_{2}}}{2} \right)\]. The equation of the chord in terms of its mid-point is\[T=S\]. or            \[x\left( \frac{{{y}_{1}}+{{y}_{2}}}{2} \right)+y\left( \frac{{{x}_{1}}+{{x}_{2}}}{2} \right)\]                 \[=2\left( \frac{{{x}_{1}}+{{x}_{2}}}{2} \right)\left( \frac{{{y}_{1}}+{{y}_{2}}}{2} \right)\] \[x({{y}_{1}}+{{y}_{2}})+y({{x}_{1}}+{{x}_{2}})=({{x}_{1}}+{{x}_{2}})({{y}_{1}}+{{y}_{2}})\]                 \[\frac{x}{{{x}_{1}}+{{x}_{2}}}+\frac{y}{{{y}_{1}}+{{y}_{2}}}=1\]


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