Results 1 to 4 of 4

Math Help - I need help understanding quadratic funtions.

  1. #1
    Newbie
    Joined
    Sep 2009
    Posts
    1

    Question I need help understanding quadratic funtions.

    How do you find the axe of symetry, summit, and minimum/maximum from two points on a parabola? Example, the points (5,-2) and (-9,-2) are on a parabola. What is the summit? How do you find it?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,130
    Thanks
    1012
    Quote Originally Posted by greenious View Post
    How do you find the axe of symetry, summit, and minimum/maximum from two points on a parabola? Example, the points (5,-2) and (-9,-2) are on a parabola. What is the summit? How do you find it?
    you can't find all that information with just two points ... unless you know the value of the leading coefficient for the parabola's equation.

    you can find the axis of symmetry ... since (5,-2) and (-9,-2) have the same y-value, the axis of symmetry will split the x-values. the equation for the axis of symmetry is ...

    x = \frac{-9+5}{2} = -2<br />
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Joined
    Mar 2007
    Posts
    1,240

    Exclamation

    I will guess that, by "summit", you mean "vertex". However, without more information, I'm afraid there is no way to find "the" quadratic through the two points.

    The x-value of the vertex will be exactly midway between the x-value of the two listed points, since their y-values are the same. But there is no way to be sure of the y-value of the vertex, or if the vertex is a maximum or a minimum. Sorry.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Sep 2009
    From
    Minnesota
    Posts
    80
    Thanks
    8
    You can only find the axis of symmetry, as stated.
    As an example, try graphing y = x^2 - 9 and y = \frac{1}{2}x^2 - 4 on the same set of axes. At y = 1, you'll notice that the points (-2\sqrt{2},1) and (2\sqrt{2},1) belong to both graphs.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Understanding quadratic equation
    Posted in the Algebra Forum
    Replies: 7
    Last Post: April 25th 2011, 11:11 AM
  2. graph funtions
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: April 3rd 2008, 05:54 PM
  3. quadratic/cubic funtions expanation
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: November 21st 2007, 09:52 PM
  4. Need help with funtions and quadratics
    Posted in the Pre-Calculus Forum
    Replies: 6
    Last Post: July 31st 2007, 04:05 PM
  5. inverse funtions
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: October 24th 2006, 07:00 AM

Search Tags


/mathhelpforum @mathhelpforum