Multiple Choice Question (MCQ)

A parabola with a vertical axis has its vertex at the origin and passes through point (7,7). The parabola intersects line y = 6 at two points. The length of the segment joining these points is

  1. ×

    14

  2. 13

  3. ×

    12

  4. ×

    8.6

  5. ×

    6.5

Collected in the board: Quadratic function

Steven Zheng posted 2 weeks ago


Answer

  1. Since it has its vertex at the origin, the parabola has the following expression

    y =kx^2

    Since it passes through point (7,7),

    k=7/7^2=1/7

    y = x^2/7

    The parabola intersects line y = 6 at two points.

    6 =x^2/7

    x=\pm\sqrt{42}

    The length of the segment joining these points is

    l = 4\sqrt{7} \approx 13


Steven Zheng posted 2 weeks ago

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