# Homework Help: Inverse matrix word problem, matrix arithmetic

1. Sep 28, 2014

### IrinaK.

1. The problem statement, all variables and given/known data
Hello!
Please, take a look at the attached picture - there is a quote of the exercise and below is my attempt to make a matrix. Is my matrix correct? I have tried many times to convert it to inverse one, but I can't figure out how to do it - I keep getting "inconvenient" numbers that do not further lead to correct answers for x, y and z.

Thank you!

2. Relevant equations

3. The attempt at a solution

#### Attached Files:

• ###### Screen Shot 2014-09-28 at 12.51.33 PM.png
File size:
52.4 KB
Views:
197
2. Sep 28, 2014

### Ray Vickson

Do not post thumbnails; they cannot be read on some media. Just type out the problem and your solution work; it should not take long and is not much trouble.

3. Sep 28, 2014

### HallsofIvy

Your set up is correct. Do you not know how to invert a matrix, say, by "row operations"? You say you get "inconvenient numbers". Do you mean just awkward fractions? The fact that the arithmetic is hard shouldn't stop you. If nothing else, you can use decimal arithmetic on a calculator, rounding to, say, three or four decimal places.

4. Sep 28, 2014

### IrinaK.

Thank you :) Yes, you are right. It seems that I always miss a correct digit here and there. Here is what I came up with (without the last row completed)

#### Attached Files:

• ###### Screen Shot 2014-09-28 at 5.16.55 PM.png
File size:
76.2 KB
Views:
132
5. Sep 28, 2014

### IrinaK.

Actually, it was a rather big picture. Sorry about that.