Results 1 to 3 of 3

Math Help - Gaussian elimination to solve systems:

  1. #1
    Junior Member
    Joined
    Dec 2008
    Posts
    31

    Unhappy Gaussian elimination to solve systems:

    Use Gaussian elimination to solve the systems:
    2x + 3y - z = 4
    4x - 2y + 3z = -7
    -6x + 7y - 7z = 3
    x = -7.5
    y= 9.3
    z= 8.9
    Im a little stumped, the answer i got for x y and z when plugged in, do not work and are incorrect. I would post my work (around 5 or 6 steps) but I trashed it after finding out it was wrong therefore losing it..
    Would anyone be willing to show me step for step how to solve this problem?
    thanks so much!!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Sep 2008
    Posts
    31
    Are you sure you typed that correctly? I couldn't solve it and when I entered it into my calculator it said there were no solutions.
    Follow Math Help Forum on Facebook and Google+

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

    Talking

    Quote Originally Posted by Murphie View Post
    Use Gaussian elimination to solve the systems:
    2x + 3y - z = 4
    4x - 2y + 3z = -7
    -6x + 7y - 7z = 3
    Unfortunately, since you did not show your work, it is not possible to help you find where you might have gone wrong. Sorry!

    There are any number of ways to approach this. Since the determinant is zero, obviously this will not have a unique solution. The only remaining question is whether there is an infinite solution (with a row of the reduced-row echelon form being all zeroes) or no solution (with a row being nonsense, like 0x + 0y + 0z = 12).

    To find out, we do row operations. There are any number of ways to proceed. The following is one:

    [html] 2x + 3y - z = 4
    4x - 2y + 3z = -7
    -6x + 7y - 7z = 3

    -2R1 + R2 -> R2
    3R1 + R3 -> R3

    2x + 3y - z = 4
    - 8y + 5z = -15
    16y - 10z = 15

    2R2 + R3 -> R3

    2x + 3y - z = 4
    - 8y + 5z = -15
    0 = -15[/html]
    What does this tell you?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: January 11th 2012, 11:57 PM
  2. Replies: 1
    Last Post: December 1st 2009, 12:13 AM
  3. Replies: 0
    Last Post: October 8th 2008, 08:58 PM
  4. Solve matrices using Gaussian elimination or...
    Posted in the Advanced Algebra Forum
    Replies: 4
    Last Post: May 4th 2007, 08:33 PM
  5. Replies: 3
    Last Post: October 11th 2006, 10:15 PM

Search Tags


/mathhelpforum @mathhelpforum