Which is the directrix of a parabola with equation x squared is equal to 4 y ?
Answer
A
y is equal to 1
B
x is equal to 1
C
y is equal to negative 1
D
x is equal to negative 1
Explanation
Compare x² = 4y with the standard form x² = 4py. Here, 4p = 4, so p = 1; the vertex is (0, 0) and the directrix is y = −p. Therefore the directrix is y = −1, choice C.
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