Which numbers are real numbers?
2 answers:
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Answer:
Step-by-step explanation:
This is a positive parabola so it opens upwards. The equation for the directrix of this parabola is y = k - p. k is the second number in the vertex of the parabola which is (0, 0), but we need to solve for p.
The form that the parabola is currently in is
so that means that
. We can use that to solve for p in the formula
so
which simplifies to
which gives us that
p = 2. Now to find the directrix:
y = k - p becomes
y = 0 - 2 so
y = -2, choice A.