JEE Main & Advanced Mathematics Conic Sections Question Bank Mock Test - Conic Sections

  • question_answer
    The vertex of a parabola is the point, (a,b) and the latus rectum is of length, l. the axis of the parabola is parallel to the y-axis and the parabola is concave upward, then its equation is

    A)  \[{{(x+a)}^{2}}=\frac{1}{2}(2y-2b)\]

    B)  \[{{(x-a)}^{2}}=\frac{1}{2}(2y-2b)\]

    C)  \[{{(x+a)}^{2}}=\frac{1}{4}(2y-2b)\]

    D)  \[{{(x-a)}^{2}}=\frac{1}{8}(2y-2b)\]

    Correct Answer: A

    Solution :

    [a] The parabola having the axis parallel to the y-axis is \[{{(x-a)}^{2}}=4A(y-b)\] According to the question, the length of latus rectum is 4A=1. Hence, the equation of the parabola is \[{{(x-a)}^{2}}=1(y-b)\] Or \[{{(x-a)}^{2}}=\frac{1}{2}(2y-2b)\]


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