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Homework Help: Matrix Transformations

  1. Oct 20, 2011 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Well guys, this is a problem I've been having for the last 2 days and with my midterm tomorrow I have no time to fiddle around with it.

    So, I do not understand how (where it says b) how

    Im going to use a division symbol ( / ) for indicating a break in the line.

    (3x+5y)[1 / -2] + (4x+7y)[-1 / 1] is equal to [-x-2y / -2x-3y]

    I have no understanding of this, because if you think of [x / y] which means it should be [(3(1) + 5(-2)) / (4(-1) + 7(1))]

    which is equal to [3x-10y / -4x+7y] which is not equal what the answer is.

    I hope you understand what I am asking and need a response asap, thanks in advance!
  2. jcsd
  3. Oct 20, 2011 #2


    Staff: Mentor

    No. It means that (3x + 5y) is a scalar that multiplies each component of the vector <1, -2>T. Here T means transpose. I'm writing a column vector as a row vector. So you get the vector <3x + 5y, -6x - 10y>T

    Same with (4x + 7y). It multiplies each component of <-1, 1>T.

    Now add the two vectors together and you should get <-x - 2y, -2x - 3y>T.
  4. Oct 20, 2011 #3
    AHHH! Hahaha, I'm stressing to much! Thank you so much! Finally, finished Matrix Transformations. Well studying it :D
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