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Calculus II Prob. Find equation of parabola and it directrix.?
Find an equation of the parabola that has a focus at (8,10) and a vertex at (8,9).
I got the answer y=1/4((x-8)^2)+9
Find an equation of its directrix.
I assume the answer is -1 for the directrix but it says its wrong. Anyone got the right answer? and how?
1 Answer
- DWReadLv 71 decade agoFavorite Answer
y = a(x-h)² + k
vertex (8, 9)
h=8, k=9
focus (8, 10)
k+p = 10
p = 1
a = 1/(4p)
= 1/4
The equation becomes
y = (1/4)(h-8)² + 9
directrix y = k-p = 8
