# Solving for a Matrix

1. Mar 8, 2012

### TranscendArcu

1. The problem statement, all variables and given/known data

3. The attempt at a solution

I think I'm oversimplifying this problem. Why can't I just write:

AX + B =CA
X + A'B = C
X = C - A'B

?

2. Mar 8, 2012

### lanedance

does your notation mean $A' = A^{-1}$?

... if so, you can't do what you propse because matrix multiplication does not necesarrily commute. ionce you fix that, you're not far off the answer

3. Mar 8, 2012

### TranscendArcu

Yes, that's what I intended my notation to convey.

Do I have to write:

AX + B = CA
AX = CA - B
A'(AX) = A'(CA - B)
IX = A'CA - A'B
X = A'CA - A'B

?

4. Mar 10, 2012

### lanedance

that looks better

5. Mar 11, 2012

### Staff: Mentor

The notation A' is sometimes used to mean the transpose of matrix A. For inverses, I don't think I've ever seen ' used to indicate the inverse.

It's just as easy to write an exponent of -1 as an exponent of 2 or 3, and the intent is much clearer.

At the bottom of the input pane, click the Go Advanced button. This opens a menu of icons at the top of the input pane. The X2 button lets you write exponents, which it does by inserting [ sup ] and [ /sup ] tags (without the spaces).

You can also do this manually, like so: A[noparse]-1[/noparse]. I have inserted some other tags so that you could see the sup tags. Without those other tags, what I wrote renders like this: A-1.