Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Matrice, solving the system, need to put it in right form!

  1. Sep 18, 2005 #1
    Hello everyone I had this system:
    -2x1 + x2 = 5
    6x1 - 3x2 = -15
    [tex]\left( {\begin{array}{*{20}c}
    {-2} & 1 & 5 \\
    6 & -3 & {-15}\\
    \end{array} } \right)[/tex]

    I then solved it down too:
    [tex]\left( {\begin{array}{*{20}c}
    {-2} & 1 & 5 \\
    0 & 0 & 0\\
    \end{array} } \right)[/tex]

    It wants me to put it parametric form:
    so i did the following:
    -2x1 + x2 = 5
    2x1 = -5 + x2
    x1 = (-5+x2)/2
    let x2 = s;
    [-5/2] + [1/2] S
    [0 ] [0 ]

    but its wrong! any ideas? Thanks
     
  2. jcsd
  3. Sep 19, 2005 #2

    TD

    User Avatar
    Homework Helper

    You have to be careful, when you let [itex]x_2 = s[/itex], it doesn't just disappear/become zero. You still have then:

    [tex]\left\{ \begin{gathered}
    x_1 = \frac{{ - 5 + x_2 }}
    {2} \hfill \\
    x_2 = x_2 \hfill \\
    \end{gathered} \right. \Leftrightarrow \left\{ \begin{gathered}
    x_1 = \frac{1}
    {2}s - \frac{5}
    {2} \hfill \\
    x_2 = s \hfill \\
    \end{gathered} \right[/tex]

    Can you get the correct vector-notation now?
     
  4. Sep 21, 2005 #3
    awsome, thanks again TD!
     
  5. Sep 21, 2005 #4

    TD

    User Avatar
    Homework Helper

    No problem :smile:
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook