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Math Help - Find expressions for the quadratic functions

  1. #1
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    Find expressions for the quadratic functions

    Find expressions for the quadratic functions whose graphs are shown:

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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by question111 View Post
    Find expressions for the quadratic functions whose graphs are shown:

    there are several ways to approach this. here's one

    note that the vertex is on the x-axis, that is, we have a double root for the vertex

    thus, our quadratic is of the form y = a(x - 3)^2

    we are given that the point (4,2) is on the graph, we can use this to find a, by plugging in x = 4 and y = 2 into the form above

    what is your answer?
    Last edited by Jhevon; January 31st 2009 at 05:56 PM.
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  3. #3
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    Quote Originally Posted by question111 View Post
    Find expressions for the quadratic functions whose graphs are shown:

    Your image is so small that it is very hard to see the co-ordinate of vertex and a point in parabola. Please write these coordinates, then it will be solved.
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Shyam View Post
    Your image is so small that it is very hard to see the co-ordinate of vertex and a point in parabola. Please write these coordinates, then it will be solved.
    if you click on the image, it takes you to a larger one
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  5. #5
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    So a would be 2, and when I plug that in, I am finally getting a graph like it's shown in the book.

    Thank you very much.
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by question111 View Post
    So a would be 2, and when I plug that in, I am finally getting a graph like it's shown in the book.

    Thank you very much.
    yes, a = 2, that's your quadratic
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  7. #7
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    and so what is your expression

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    Quote Originally Posted by lovegreen View Post
    i do not understand your question. we found that a = 2. just plug that into the expression given in post #2 to get the quadratic
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  9. #9
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    Smile Thanks!

    I see it is y = 2(x squared) -12x + 18
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  10. #10
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    Quote Originally Posted by lovegreen View Post
    I see it is y = 2(x squared) -12x + 18
    Why not just leave it as y= 2(x- 3)^2?
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