CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2004

  • question_answer
    The condition that\[ax+by+c=0\]is tangent to the parabola\[{{y}^{2}}=4ax,\]is:

    A)  \[{{a}^{2}}={{b}^{2}}={{c}^{2}}\]             

    B)  \[a=b\]

    C)  \[{{b}^{2}}=c\]                

    D)        \[{{b}^{2}}=a\]

    E)  \[{{a}^{2}}=b\]

    Correct Answer: C

    Solution :

    The equation of line is \[ax+by+c=0\] \[\Rightarrow \]               \[y=-\frac{a}{b}x-\frac{c}{b}\] Thus, this line will be tangent to the parabola \[{{y}^{2}}=4ax\]is \[-\frac{c}{b}=\frac{a}{-\frac{a}{b}}\Rightarrow c={{b}^{2}}\]


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