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anonymous

  • one year ago

Derive the equation of the parabola with a focus at (−2, 4) and a directrix of y = 6. Put the equation in standard form. f(x) = one fourthx2 − x + 4 f(x) = −one fourthx2 − x + 4 f(x) = one fourthx2 − x + 5 f(x) = −one fourthx2 − x + 5

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  1. anonymous
    • one year ago
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    @Elsa213

  2. freckles
    • one year ago
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    |dw:1439322589152:dw|

  3. freckles
    • one year ago
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    the distance from the point (x,y) to the focus is suppose to be equal to the distance from the point (x,y) to the directrix

  4. freckles
    • one year ago
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    setup this equation

  5. freckles
    • one year ago
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    and play with eventually you should get the form mentioned in your choices

  6. anonymous
    • one year ago
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    is c correct

  7. anonymous
    • one year ago
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    @freckles

  8. campbell_st
    • one year ago
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    C can't be correct as the parabola is concave down... so the coefficient of x^2 is needs to be negative

  9. freckles
    • one year ago
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    did you try setting up the equation? I'm not sure why they ask you to derive it when it is multiple choice because you don't really need to derive the formula if is multiple choice odd but yep the way I mentioned is to derive the equation set the two distances I talked about equal to each other

  10. anonymous
    • one year ago
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    @campbell_st is it b

  11. campbell_st
    • one year ago
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    why guess.... learn a little... but this is what I'd do... |dw:1439322785572:dw|

  12. campbell_st
    • one year ago
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    the vertical dotted line is the line of symmetry

  13. anonymous
    • one year ago
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    so d is correct thanks :)

  14. anonymous
    • one year ago
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    @campbell_st

  15. campbell_st
    • one year ago
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    is it... I have no idea... I haven't calculated anything...

  16. anonymous
    • one year ago
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    can you calucute then ? @campbell_st

  17. freckles
    • one year ago
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    @jammy987 did you not want to try to set the two distances I talked about equal to each other?

  18. campbell_st
    • one year ago
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    sure what is the vertical distance from the focus to the directrix...?

  19. anonymous
    • one year ago
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    4 correct

  20. anonymous
    • one year ago
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    and @freckles ikust need the answer sorry

  21. campbell_st
    • one year ago
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    no have a look again... the focus has a y value of y = 4 the directrix is at y = 6 how far apart are the y values...?

  22. freckles
    • one year ago
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    ok you can count me out then have fun

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