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.
