Question

Select the graph that correctly represents ƒ(x) = –2(x + 4)2 – 1.Find the equation of the parabola with its focus at (3,4) and its directrix y = 0.

Answer 1

Answer:

Equation of parabola:  8*(y - 2) = (x - 3)^2

or

y = (1/8)*(x - 3)^2 + 2

Step-by-step explanation:

focus at (3,4) and its directrix y = 0.

Focus equation:  (h, k + c) = (3, 4)

Directrix equation  y =  k - c = 0

so  h = 3,   k + c = 4,   k - c = 0

Solve  the system :  k + c = 4 and k - c = 0

add the equations together:     k + c + k - c = 4 + 0

2k = 4

k = 2

so   k + c = 4,    2 + c = 4,   c = 2

4c (y - k) = (x -  h)^2

4*2 *(y - 2) = (x - 3)^2

8*(y - 2) = (x - 3)^2