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Parabolas

Question 2 • *CR CCSS Math 2 S2 [M2960OX]

Which statements are true for the equation x2 = −4y? Check all that apply.The axis of symmetry is x = 0.The focus is at (0, –1).The parabola opens up.The parabola opens right.The value of p = −1.The equation for the directrix is y = 0.

Answer
A
The axis of symmetry is x = 0.
B
The focus is at (0, –1).
C
The parabola opens up.
D
The parabola opens right.
E
The value of p = −1.
F
The equation for the directrix is y = 0.

Explanation

Compare x² = −4y with the standard vertical-parabola form x² = 4py. This gives p = −1, so the axis of symmetry is x = 0 and the focus is (0, −1). Because p is negative, the parabola opens down, not up or right; its directrix is y = −p = 1, not y = 0.

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