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

Simplying a matrix equation

  1. Nov 12, 2007 #1
    x+2y y+2t = 5x -y

    4x+3z 4y+3t = 5z -t

    Iam just not sure how they simplified these equations to this:

    z = 2x, t = -y??

    Please help.
  2. jcsd
  3. Nov 12, 2007 #2


    User Avatar
    Science Advisor
    Gold Member

    Your notation is confusing. You have a blank in the first equation between 2y and y. Similarly in the second equation between 3z and 4y. What do you mean??
  4. Nov 12, 2007 #3
    The two are separate matrices

    Like one is
    x+2y y+2t
    4x+3z 4y+3t

    And the other is
    5x -y
    5z -t

    And they set them equal and simplify to

    z = 2x, t = -y

    I dont get how they got that?
  5. Nov 12, 2007 #4


    User Avatar
    Science Advisor
    Homework Helper

    You have a 4x4 matrix on the left.

    What is on the right?
  6. Nov 12, 2007 #5
    I have no 4x4

    one matrix is 2x2:

    (First column)
    (Second Column)

    Second matrix is 2x2:

    (First column)
    (Second Column)
    Last edited: Nov 12, 2007
  7. Nov 13, 2007 #6


    User Avatar
    Staff Emeritus
    Science Advisor

    Now that we have it clear that these are matrices, they must give, since two matrices are equal if and only if their corresponding entries are equal,
    x+2y= 5x, y+ 2t= -y, 4x+ 3z= 5z, and 4y+ 3t= -t.
    The third equation is just 4x= 2z (subtract 3z from both sides). Also, the fourth equation is the same as 4y= -4t (subtract 3t from both sides) so t= -y as claimed.
  8. Nov 13, 2007 #7
    Ahh I understand now... Thank you so much for the help.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Simplying a matrix equation
  1. Simply connected stuff (Replies: 13)