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anonymous
 one year ago
Find the standard form of the equation of the parabola with a focus at \((0,−9)\) and a directrix \(y=9.\)
anonymous
 one year ago
Find the standard form of the equation of the parabola with a focus at \((0,−9)\) and a directrix \(y=9.\)

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welshfella
 one year ago
Best ResponseYou've already chosen the best response.0this parabola opens upwards and standard form is x^2 = 4ay where a is the y coordinate of the focus and y = a is the directrix so can you work this one out?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Wouldn't the parabola open downwards?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0It would. The form for a parabola is \[y = 1/4p(xh)^2+k\] From here you can plug 9 into p since p = distance between vertex and focus. The h and k values are both 0 since the vertex is at (0,0). Can you get it from here?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I lied, plug 9 in for p.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0dw:1439345400610:dw

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Hang on, I'm trying to solve it. :)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Okay, post your answer here so I can check it for you :)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0So is it \(y=\frac{ 1 }{ 36 }x^2?\)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Wow thanks! I was working with this, but I got the vertex wrong. :( How would you find the vertex?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0No problem! Okay so the vertex is equidistant from both the focus and the directrix. Since they both are 9 away from the origin (as the x value for both is 0) you can tell that the vertex must be at the origin in order for it to be equidistant from both!

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Awesome! Thanks again. You're great! :)

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0yes surit is correct  i misread the problem

welshfella
 one year ago
Best ResponseYou've already chosen the best response.0 and migillope also
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