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Vertex Focus Directrix Calculus Questions

Overview

        1.     

Find the vertex, focus, directrix, and focal width of the parabola.

x2 = 12y (1 point)

                        Vertex: (0, 0); Focus: (3, 0); Directrix: x = 3; Focal width: 3

                        Vertex: (0, 0); Focus: (0, 3); Directrix: y = -3; Focal width: 12

                        Vertex: (0, 0); Focus: (3, 0); Directrix: y = 3; Focal width: 48

                        Vertex: (0, 0); Focus: (0, -3); Directrix: x = -3; Focal width: 48

        2.     

Find the vertex, focus, directrix, and focal width of the parabola.

x = 3y2 (2 points) 

                        Vertex: (0, 0); Focus: one divided by twelve comma zero ; Directrix: x = one divided by twelve ; Focal width: 12

                        Vertex: (0, 0); Focus: the point one twelfth comma zero ; Directrix: x = negative one twelfth ; Focal width: 0.33

                        Vertex: (0, 0); Focus: zero comma one divided by sixteen ; Directrix: x = negative one divided by sixteen ; Focal width: 0.33

                        Vertex: (0, 0); Focus: one divided by sixteen comma zero ; Directrix: y = nnegative one divided by sixteen ; Focal width: 12

        3.     

Find the standard form of the equation of the parabola with a vertex at the origin and a focus at (0, -7). (1 point)

                        y = negative one divided by seven x2

                        y2 = -7x

                        y = negative one divided by twenty eight x2

                        y2 = -28x

        4.     

Find the standard form of the equation of the parabola with a focus at (0, 8) and a directrix at y = -8. (2 points)

                        y = one divided by thirty two x2

                        y2 = 8x

                        y2 = 32x

                        y = one divided by eight x2

        5.     

Find the standard form of the equation of the parabola with a focus at (7, 0) and a directrix at x = -7. (2 points)

                        y = one divided by twenty eight x2

                        x = one divided by twenty eight y2

                        -28y = x2

                        y2 = 14x

        6.     

   A building has an entry the shape of a parabolic arch 96 ft high and 18 ft wide at the base, as shown below.