At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
Answer Choices: A. y = -1/9x^2 B. y^2 = -36x C. y = -1/36x^2 D. y^2 = -9x
What do you think the answer is? Do you know what a focus is?
What's the formula for parabola? How can you plug it into the formula?
The formula is (x−h)^2=4p(y−k)
@tom982 Where (h,k) is the vertex
and focus is either (h, k+p) or (h+p ,k)
That's all I know
Let's work through it with the material you provided. \[ (x−h)^2=4p(y−k)\] focus at \( (0, -9)\) and directrix of \(y = 9\) Any idea where the vertex will be?
I don't know
I don't know how to get the vertex from that information.
yo, @turmoilx2 are you going to take part here?
Yes. I am replying. @whpalmer4
I just don't see what I'm supposed to do with the information yet.
Do you know the definition of what a parabola is? It is a set of points that satisfy some rule, do you know what the rule is?
sorry, open study is not behaving well for me, going to try restarting my browser, brb...
I'd suggest that you attempt to graph this parabola. Draw a set of axes and locate the given point and the given line. Identify the point, the line and the vertex of your parabola. Even a quick sketch would be helpful. Your job will be to relate distances in this drawing to the equation of a parabola. What does "p" in your formula represent? If you're not sure, look it up, please. Try the Internet and search for "equations of a parabola." Your graph should give you the value of p by inspection.
OS is not behaving well for me either. That is why I haven't been participating in the solving of my question.
Important: The vertex of a parabola lies exactly halfway between the directrix (a line) and the focus (a point). If the directrix is the horiz. line y=9 and the focus is at (0,-9), what are the coordinates of the vertex? Again, I ask you to graph this situation. Show the directrix, the focus and the vertex.
|dw:1449542174879:dw| Here's my sketch
Please see the following on the 'Net: https://www.google.com/search?sourceid=chrome-psyapi2&ion=1&espv=2&es_th=1&ie=UTF-8&q=directrix%20parabola&oq=directrix%20parabola&aqs=chrome..69i57j0l5.3199j0j7 The very first illustration shows that the vertex is halfway between the directrix and the focus. p is the distance between the focus and the vertex. What is p here?
Will YOUR parabola open up or down? You are given the directrix: y=9, and the focus: (0,-9). The vertex is in between. UP or DOWN?