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-   -   Solving Quadratic Equations to Graph (https://www.askmehelpdesk.com/showthread.php?t=16414)

  • Dec 23, 2005, 10:53 AM
    phoenirius
    Solving Quadratic Equations to Graph
    How would I graph x^2-3x=4 to solve it?
    And I would I check?
    Thank You.
  • Dec 23, 2005, 11:53 AM
    reinsuranc
    Graphing
    Start with the quadratic in the form y = a*x^2 + b*x + c.

    If a>0, the parabola is U-shaped; if a<0, the parabola is upside-down u-shaped.

    If a>0, the minimum y value is at the point called the vertex. (If a<0, the maximum
    y value is at the point called the vertex.) The vertex (h,k) is found by
    calculating h = -b/(2a), and then substituting that x value to find the corresponding
    y value for k.

    y = x^2 - 3x -4.

    a=1, b=-3.

    h = -b/(2a) = --3/(2*1) = +3/2

    y = k = (3/2)^2 - 3*(3/2) -4 = -25/4.

    So minimum y point is at (3/2, -25,4).

    Also find the y-intercept where x=0: y = 0^2 - 3*0 -4 = -4.

    Now just plug in various x values and graph. Try x=1, x=2, x=3, x=4, x=-1. x=-2. x=-3. x=-4.
  • Apr 26, 2007, 03:40 PM
    Kenneth Greene
    3x^2-5x-2
  • Apr 26, 2007, 04:33 PM
    galactus
    Why are you posting on a topic which was posted almost a year and a half ago? How about starting your own thread?

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