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sloppycanada

  • one year ago

Write the equation of a parabola with a vertex at (-5, 2) and a directrix y = -1.

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  1. sloppycanada
    • one year ago
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    \[x+5 = \frac{ 1 }{ 12 }(y-2)^2\]

  2. amoodarya
    • one year ago
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    directix is y=-1 so parabola is vertical (x+5)^2=4p(y-2)

  3. sloppycanada
    • one year ago
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    Oh so I find 'p' now?

  4. anonymous
    • one year ago
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    Do you have any question choices? sorry haven't done these in a long time lol

  5. sloppycanada
    • one year ago
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    http://gyazo.com/92c75a607eefcd67e67bf08e7368c6fa

  6. anonymous
    • one year ago
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    I remember now! So we first put it in vertex form. Typical vertex form is ;\[y=a(x-h)^2+k\]

  7. anonymous
    • one year ago
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    Keep in mind that h is x, and k is y, so \[(h,k) = (x,y)\]

  8. anonymous
    • one year ago
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    this seems hard lol

  9. anonymous
    • one year ago
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    So we have the vertex (and forgot to mention, that h,k is the vertex) (-5,2)

  10. sloppycanada
    • one year ago
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    Yup! And since it's not at (0,0) it means I have to add things. If I remember correct, it's the opposite sign that you're supposed to use.

  11. anonymous
    • one year ago
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    we put them in, and now we get what?

  12. sloppycanada
    • one year ago
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    x+5 = (y-2)^2

  13. sloppycanada
    • one year ago
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    But I still need the 4p

  14. anonymous
    • one year ago
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    \[y=a(x+5)^2-2\]

  15. anonymous
    • one year ago
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    Well we still have to find a, and note the answer choice that you picked is wrong :/

  16. sloppycanada
    • one year ago
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    Which is something to do with "p"

  17. anonymous
    • one year ago
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    hold on a sec...

  18. sloppycanada
    • one year ago
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    Okay...?

  19. anonymous
    • one year ago
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    SO a is the slope

  20. anonymous
    • one year ago
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    Or the the rate of change

  21. Loser66
    • one year ago
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    @amoodaray gave you the equation, why do you go on the complex way?

  22. sloppycanada
    • one year ago
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    I'm not sure how to find 'p'

  23. Loser66
    • one year ago
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    Is it not that "directrix y =-1" given?? and it gives you p = 1?? am I right?

  24. Loser66
    • one year ago
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    |dw:1435884812050:dw|

  25. sloppycanada
    • one year ago
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    Oh yeah..in that case... then my answer should be 1/4

  26. Loser66
    • one year ago
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    and the equation of parabola is x^2 =4py in your case, just put the vertex in

  27. Loser66
    • one year ago
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    yyyyyyyyyyyyes

  28. sloppycanada
    • one year ago
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    x+5^2 = 1/4(y-2)^2?

  29. Loser66
    • one year ago
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    Nope

  30. Loser66
    • one year ago
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    \((x+5)^2=4(y-2)\) open parentheses

  31. sloppycanada
    • one year ago
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    But that isn't one of my options...

  32. Loser66
    • one year ago
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    \((x^2+10x+25) = 4y -8\)

  33. Loser66
    • one year ago
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    \(4y=x^2+10x+33\) divide both sides by 4 what are your options?

  34. sloppycanada
    • one year ago
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    http://gyazo.com/92c75a607eefcd67e67bf08e7368c6fa

  35. Loser66
    • one year ago
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    hey, they don't open parentheses and our answer is b,

  36. Loser66
    • one year ago
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    \((x+5)^2=4(y-2)\) divide both sides by 4, you get b

  37. sloppycanada
    • one year ago
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    Okay.. Thanks!

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