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anonymous

  • one year ago

A parabola has its vertex at the origin and a directrix at y=4. Where is the focus located?

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  1. jim_thompson5910
    • one year ago
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    blank xy axis |dw:1437436785171:dw|

  2. jim_thompson5910
    • one year ago
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    |dw:1437436834898:dw|

  3. jim_thompson5910
    • one year ago
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    draw in the directrix y = 4 |dw:1437436852839:dw|

  4. jim_thompson5910
    • one year ago
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    `A parabola has its vertex at the origin` |dw:1437436941427:dw|

  5. jim_thompson5910
    • one year ago
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    how far is the vertex from the directrix?

  6. anonymous
    • one year ago
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    4 spaces

  7. anonymous
    • one year ago
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    @jim_thompson5910 4 spaces

  8. jim_thompson5910
    • one year ago
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    correct

  9. jim_thompson5910
    • one year ago
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    we move 4 spaces in the opposite direction to get to the focus |dw:1437437123551:dw|

  10. jim_thompson5910
    • one year ago
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    The focus is always located on the axis of symmetry. The axis of symmetry is the line perpendicular to the directrix and it passes through the vertex In this case, the axis of symmetry lies on top of the y axis |dw:1437437233976:dw|

  11. anonymous
    • one year ago
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    Ohhh I understand now! Thank you! So my focus is located at (0,-4)

  12. jim_thompson5910
    • one year ago
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    correct

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