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Math Help - Understanding Parabola's

  1. #1
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    Understanding Parabola's

    I come to you with the need for some help....I'm an online student and have no assistance from the book in regards to this question;
    Write an equation for a parabola that opens downward and has a vertex of (0,4)....as you see from my name this subject is not my strong suit....

    My answer to this problem is simply y=0.0x-1.5 (I really don't feel to strongly that this is correct) thus is why I am here!

    Thanks,
    BAS
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  2. #2
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    Re: Understanding Parabola's

    There are infinitely many of course. One such would be y=4-x^2
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    Re: Understanding Parabola's

    Quote Originally Posted by BetterAtScience View Post
    I come to you with the need for some help....I'm an online student and have no assistance from the book in regards to this question;
    Write an equation for a parabola that opens downward and has a vertex of (0,4)....as you see from my name this subject is not my strong suit....

    My answer to this problem is simply y=0.0x-1.5 (I really don't feel to strongly that this is correct) thus is why I am here!
    In general, a parabola with a vertical axis is given by the equation

    (x - h)^2 = 4p(y-k)

    where (h, k) is the vertex and p is the directed distance from the vertex to the focus.

    We want a vertex of (0,4), so substitute these values for h and k:

    (x - 0)^2 = 4p(y-4)

    \Rightarrow x^2 = 4p(y - 4)

    \Rightarrow y = \frac1{4p}x^2 + 4

    \Rightarrow y = ax^2 + 4,

    where a = \frac1{4p} is a constant. Choose any nonzero value for a and you will get a parabola with a vertex at (0, 4). For the parabola to open downward, choose a<0.
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  4. #4
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    Re: Understanding Parabola's

    That seems to make is a little clearer, I appreciate the assistance....I feel ackward asking for help since I already have Nursing degree and decided to go back to school this summer as sort of a mid-life crisis! Thank you for being here.....if you got a illness I can return the favor!!!!
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