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ANSWER

A. Directrix y=-5, focus; (-2,6)

EXPLANATION

  • In other to figure out the parabola that opens up we need to know the relation between the directrix and focus.
  • The focus is always inside the parabola and the directrix is always outside.
  • If the directrix is above the focus,the parabola opens downwards.
  • If the directrix is below the focus, the parabola opens upwards.
  • How do you determine whether the directrix is above or below.
  • You just have to compare the y-value of the focus to the directrix because the orientation is parallel to the y-axis
  • For the first option, the directrix y=-5 is below the focus (-2,6).
  • Since the focus must lie inside the parabola, this parabola must open up.
  • For the second option, the directrix, y=-5 is above the focus (2,-6). This parabola opens downwards.
  • For the third option, the directrix, y=5 is above the focus (-6,-2). This parabola opens downwards.
  • For the second option, the directrix, y=5 is above the focus (6,2). This parabola opens downwards.

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