JCECE Engineering JCECE Engineering Solved Paper-2008

  • 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

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

    B) \[x-y+2=0\]

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

    D) \[x+y+2=0\]

    Correct Answer: A

    Solution :

    The equation of given straight line is                 \[y-x+5=0\]                 \[y=x-5\]                                             ? (i) The equation of any straight line parallel to the given straight line will be                 \[y=x+c\]             \[(\because \,\,m=1)\]  ... (ii) This straight line will be tangent to the given hyperbola                 \[\frac{{{x}^{2}}}{3}-\frac{{{y}^{2}}}{2}=1\]                                          ? (iii) Here,\[{{a}^{2}}=3,\,\,{{b}^{2}}=2\],                 \[{{c}^{2}}={{a}^{2}}{{m}^{2}}-{{b}^{2}}\] \[\Rightarrow \]               \[{{c}^{2}}=3\cdot 1-2\] \[\Rightarrow \]               \[{{c}^{2}}=1\] \[\Rightarrow \]               \[c=\pm 1\] Hence, the equation of the required tangent will be                 \[y=x\pm 1\] \[\Rightarrow \]               \[y-x-1=0\]or\[y-x+1=0\] \[\Rightarrow \]               \[x-y+1=0\]or\[x-y-1=0\]


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