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Parabola Equation Help :x

So I'm in dire need for someone to help me come up with an equation with the following information given :l

I'm having a quarterly coming up soon and the teacher hinted on having 2 of these types of questions on the test. I do not have a clue as to how to even start, and I was hoping someone may clear it up for me nicely!

The information given is:

Axis: Parallel to y-axis

Passes through the points:
(0,3) , (3,4) , (4,11)

Directions are to find the equation of the specified parabola.

If someone could show me the steps as well that would be greatly appreciated.

November 12, 2010

11 Comments • Newest first

radkai

I explained everything I could. Look through my posts and do everything I said. There should be no uncertainty on how to do this problem.

Reply November 12, 2010
hyj1106

[quote=radkai]I go to Stuyvesant High School. (aka the top high school of New York City, google/wikipedia can prove this)[/quote]

I know what it is. I go to Horace Mann lol.

Reply November 12, 2010
radkai

[quote=hyj1106]What kinda school do you go to? We don't have resource websites lol[/quote]

I go to Stuyvesant High School. (aka the top high school of New York City, google/wikipedia can prove this)

Reply November 12, 2010
hyj1106

[quote=Billionz]If the textbook doesn't explain everything, never forget to use the resource websites that the school has provided for you.[/quote]

What kinda school do you go to? We don't have resource websites lol

Reply November 12, 2010
Billionz

If the textbook doesn't explain everything, never forget to use the resource websites that the school has provided for you.

Reply November 12, 2010
radkai

[quote=PandorasBox]About the (0,3) being the lowest point? o.o[/quote]

Of course.

Reply November 12, 2010
radkai

[quote=PandorasBox]It's pretty simple really.
(0,3) is the vertex of the parabola because you can see those two other points are on one side of the axis and continue to grow while (0,3) is the lowest point.
Then graph (3,4) and (4,11). Then procede to flip them over the y-axis and draw the parabola.
As for the equation of a vertex equation of a parabola is: a(x-h)^2+k. Where -h = x and k=y of the vertex. I don't really know how you would find "a" or how to put it into standard form but I think that's a good start for you.[/quote]

Incorrect assumption!

@hyj1106 dude.... a=5/3 b=-14/3 Put those numbers in the standard form of a quadratic equation. 5x^2/3-14x/3+3=y

Reply November 12, 2010 - edited
hyj1106

[quote=radkai]You don't know how to do systems? o.o 1st equation you get 1=9a+3b. 2nd you get 2=4a+b. Multiply the 2nd equation by -3 to get -6=-12a-3b. Combine the two equations. -5=-3a. a=5/3 Plug 5/3 back into any equation. 2=20/3 +b. b=-14/3[/quote]

OKay I got that much done, I did know how to do them but I wasn't exactly sure.

Uhm, so how would I proceed after this?

Reply November 12, 2010 - edited
radkai

[quote=hyj1106]The given information is

Axis: Parallel to y-axis
Passes through the points: (0,3), (3,4), and (4,11)

Exactly verbatim. :x

@Above: what do I do next? I"m seriously clueless[/quote]

You don't know how to do systems? o.o 1st equation you get 1=9a+3b. 2nd you get 2=4a+b. Multiply the 2nd equation by -3 to get -6=-12a-3b. Combine the two equations. -5=-3a. a=5/3 Plug 5/3 back into any equation. 2=20/3 +b. b=-14/3

Reply November 12, 2010 - edited
hyj1106

The given information is

Axis: Parallel to y-axis
Passes through the points: (0,3), (3,4), and (4,11)

Exactly verbatim. :x

@Above: what do I do next? I"m seriously clueless

Reply November 12, 2010 - edited
radkai

y=ax^2+bx+c c=3 because it passes through (0,3) now plug in the other points. 4=9a+3b+3 (3,4) 11=16a+4b+3 (4,11) you got system of equations

Reply November 12, 2010 - edited