1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Matrix Multiplication or Inverse Problem

  1. May 6, 2012 #1
    1. The problem statement, all variables and given/known data

    I am more trying to figure out how to solve generally rather than solve this specific problem. Nevertheless this problem could be given as: Solve the matrix for A and B.

    2. Relevant equations


    [tex]\begin{pmatrix}
    1 & 1 \\
    0 & 0 \\
    0 & 2 \\
    2 & 0 \\
    0 & 0 \\
    \end{pmatrix}
    \begin{pmatrix}
    A \\
    B
    \end{pmatrix}=
    \begin{pmatrix}
    42 \\
    0 \\
    0 \\
    8 \\
    50 \\
    \end{pmatrix}[/tex]

    apparently this matrix is of the form (CTC)X=CTB


    3. The attempt at a solution

    I do not understand how to solve it! In this problem, what would A=? and B=? look like? Do I have to send the first matrix to the right-hand side?

    This is just a basic example. I will later want to solve the same kind of problem where the first matrix has more columns and the second matrix has more rows.

    Thank you in advance.
     
  2. jcsd
  3. May 6, 2012 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Do you understand what matrix multiplication is? What you have is equivalent to the 5 equations, A+ B= 42, 0= 0, 2B= 0, 2A= 8 and 0= 50. A and B have to be number for "A+ B= 42", "2B= 0", and "2A= 8" to make sense. But no matter what A and B are, "0= 50" is impossible. There is NO solution to this problem.
     
  4. May 6, 2012 #3
    I mistyped the Eq. Should be

    [tex]\begin{pmatrix}
    1 & 1 \\
    0 & 0 \\
    0 & 2 \\
    2 & 0 \\
    0 & 0 \\
    \end{pmatrix}
    \begin{pmatrix}
    A \\
    B
    \end{pmatrix}=
    \begin{pmatrix}
    42 \\
    0 \\
    8 \\
    50 \\
    0 \\
    \end{pmatrix}[/tex]
     
  5. May 6, 2012 #4

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    So your answer is that you do not know how to multiply matrices?
     
  6. May 6, 2012 #5
    Well, I did come to the "homework section". Maybe I should just stop trying to learn new things.
     
  7. May 6, 2012 #6

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Okay, I tried to help- my point was that this problem is trivial once you multiply the matrices on the left. Can you do that?
     
  8. May 6, 2012 #7
    I figured it out. I kept getting nonsense so I thought I didn't know what I was doing. Turns out the values needed to be converted.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Matrix Multiplication or Inverse Problem
  1. Inverse Matrix Problem (Replies: 6)

  2. Inverse matrix problem (Replies: 13)

Loading...