77. Find the vertex and focus of the parabola.
$x^2 = 36y$
a. vertex: (0, 0) focus: (0, -9)
b. vertex: (0, 0) focus: (0, 9)
c. vertex: (0, 9) focus: (0, 0)
d. vertex: (9, 0) focus: (0, 0)
e. vertex: (-9, 0) focus: (0, 0)
78. Give the standard form of the equation of the parabola with the given characteristics.
vertex: $(-1, -3)$, focus: $(-1, -6)$
a. $(x+1)^2 = -20(y-3)$
b. $(x-3)^2 = -20(x-1)$
c. $(x-3)^2 = -20(x+1)$
d. $(x-3)^2 = -20(x-1)$
e. $(x+1)^2 = -20(y+3)$
79. A solar oven uses a parabolic reflector to focus the sun's rays at a point 6 inches from the
vertex of the reflector (see figure). Write an equation for a cross section of the oven's
reflector with its focus on the positive $y$ axis and its vertex at the origin.
$l=6$ inches
a. $y = 24x^2$
b. $y = \frac{1}{6}x^2$
c. $x^2 = 24y$
d. $y^2 = 6x^2$
e. $x^2 = 6y$
80. Identify the conic as a circle or an ellipse then find the center.
$\frac{x^2}{9} + \frac{y^2}{4} = 1$
a. Circle
Center: $(0, 0)$
b. Ellipse
Center: $(0, 0)$
