Results 1 to 5 of 5

Math Help - quadratic functions

  1. #1
    Junior Member
    Joined
    Apr 2008
    Posts
    31

    quadratic functions

    ok this is my lasst question of the night i promise!

    Find the unique quadratic function that passes through the points (-2, 5), (1,-1), and (6, 29). use matrices to solve
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    Quote Originally Posted by mamajen View Post
    ok this is my lasst question of the night i promise!

    Find the unique quadratic function that passes through the points (-2, 5), (1,-1), and (6, 29). use matrices to solve
    You need to create a sytem of equations given these 3 points.

    Use y =ax^2+bx+c

    Here's the first one (-2,5) \implies 5 = a(-2)^2+b(-2)+c = 4a-2b+c

    You do the next 2, I will then show you the next step.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Apr 2008
    Posts
    31
    Quote Originally Posted by pickslides View Post
    You need to create a sytem of equations given these 3 points.

    Use y =ax^2+bx+c

    Here's the first one (-2,5) \implies 5 = a(-2)^2+b(-2)+c = 4a-2b+c

    You do the next 2, I will then show you the next step.
    ok here is what i have.....
    (1, -1) -1=a+b+c
    (6, 29) 29=36a+6b+c
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    Quote Originally Posted by mamajen View Post
    ok here is what i have.....
    (1, -1) -1=a+b+c
    (6, 29) 29=36a+6b+c
    so we have,

    -1=a+b+c
    29=36a+6b+c
    5 = 4a-2b+c


    Which can be written in matrix form as

     <br />
\left[ \begin{array}{c}<br />
a\\<br />
b\\<br />
c\end{array}\right]=\left[ \begin{array}{ccc}<br />
1 & 1 & 1 \\<br />
36 & 6 & 1 \\<br />
4 & -2 & 1 \end{array} \right]^{-1} \left[ \begin{array}{c}<br />
-1\\<br />
29\\<br />
5\end{array}\right]<br />

    Now you need to find the inverse of a 3\times 3 matrix, will be tricky
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Apr 2008
    Posts
    31
    Quote Originally Posted by pickslides View Post
    so we have,

    -1=a+b+c
    29=36a+6b+c
    5 = 4a-2b+c


    Which can be written in matrix form as

     <br />
\left[ \begin{array}{c}<br />
a\\<br />
b\\<br />
c\end{array}\right]=\left[ \begin{array}{ccc}<br />
1 & 1 & 1 \\<br />
36 & 6 & 1 \\<br />
4 & -2 & 1 \end{array} \right]^{-1} \left[ \begin{array}{c}<br />
-1\\<br />
29\\<br />
5\end{array}\right]<br />

    Now you need to find the inverse of a 3\times 3 matrix, will be tricky
    1, -1, 1

    thanks so much for your help!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Quadratic Functions
    Posted in the Algebra Forum
    Replies: 4
    Last Post: April 19th 2009, 02:15 PM
  2. Quadratic Functions
    Posted in the Algebra Forum
    Replies: 6
    Last Post: March 2nd 2009, 12:11 AM
  3. Quadratic Functions
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: December 7th 2008, 10:20 AM
  4. Quadratic Functions
    Posted in the Pre-Calculus Forum
    Replies: 7
    Last Post: October 16th 2008, 07:01 PM
  5. Quadratic functions
    Posted in the Algebra Forum
    Replies: 3
    Last Post: November 14th 2007, 05:11 PM

Search Tags


/mathhelpforum @mathhelpforum