# I get to a dead end with the 5th part

1. Feb 6, 2008

### transgalactic

Last edited: Feb 6, 2008
2. Feb 6, 2008

### HallsofIvy

Staff Emeritus
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?

3. Feb 6, 2008

### transgalactic

ohhh thats the answer
i thought that we need toeliminate A totaly

4. Feb 6, 2008

### HallsofIvy

Staff Emeritus
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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