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Homework Help: I get to a dead end with the 5th part

  1. Feb 6, 2008 #1
    Last edited: Feb 6, 2008
  2. jcsd
  3. Feb 6, 2008 #2

    HallsofIvy

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    I had already answered this. Please stop double posting.

    You are given that A2- A= -I for linear transformation A and you are asked to find A-1. In your solution you multiply both sides by A-1 (as I had suggested before) and get A- I= -A-1. Then you do a lot of things that I don't understand.

    Just multiply on both sides by -1 to get A-1= I- A. What more do you want?
     
  4. Feb 6, 2008 #3
    ohhh thats the answer
    i thought that we need toeliminate A totaly
     
  5. Feb 6, 2008 #4

    HallsofIvy

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    Actually, way back where you had A(A- I)=-I you could have written that as A(I-A)= I and said "Since I-A, multiplying A give the identity, I-A must be the inverse of A!"
     
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