Using a directrix of y = -2 and a focus of (2, 6), what quadratic function is created?
a. f(x) = - 1/8 (x - 2)2 - 2

b. f(x) = 1/16 (x - 2)2 + 2

c. f(x) = 1/8 (x - 2)2 - 2

d. f(x) = - 1/16 (x + 2)2 - 2
@satellite73 @jim_thompson5910 @SolomonZelman @iambatman @Directrix @Callisto @Kainui @wio @TheSmartOne

Question

Using a directrix of y = -2 and a focus of (2, 6), what quadratic function is created?
a.  f(x) = - 1/8 (x - 2)2 - 2

b. f(x) = 1/16 (x - 2)2 + 2

c. f(x) = 1/8 (x - 2)2 - 2

d. f(x) = - 1/16 (x + 2)2 - 2
@satellite73 @jim_thompson5910 @SolomonZelman @iambatman @Directrix @Callisto @Kainui @wio @TheSmartOne

jim_thompson5910 · Answer

The y coord of the focus (2, 6) is y = 6

jim_thompson5910 · Answer

what is the distance from y =  -2 to y = 6 ?

anonymous · Answer

8?

jim_thompson5910 · Answer

yes

jim_thompson5910 · Answer

this is the distance from directrix to focus

cut this in half to get 8/2 = 4

4 is the distance from the vertex to the focus

anonymous · Answer

okay?

jim_thompson5910 · Answer

ie the focal distance, so p = 4

jim_thompson5910 · Answer

are you able to determine the vertex?

jim_thompson5910 · Answer

blank xy axis
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anonymous · Answer

i dont know the vertex

jim_thompson5910 · Answer

plot the directrix (horizontal line at y = -2) and focus (2,6)
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jim_thompson5910 · Answer

we know this vertical distance is 8

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