Finding the inverse example?

Question

1.

A= [5 0 2]

-----[2 2 1]

-----[-3 1 -1]

This what I have so far:

[5 0 2] --- [1 0 0] Multiply the whole row by 1/5

[2 2 1] --- [0 1 0]

[-3 1 -1] --- [0 0 1]

[1 0 .4]---[1/2 0 0]

[2 2 1]----[0 1 0] Multiply the whole row by 1/2

[-3 1-1]---[0 0 1]

[1 0 .4]----[1/2 0 0]

[1 1 ½]----[0 1 0]

[-3 1 -1]---[0 0 1] Multiply the whole row by 1/3

Don't know if I am on the right track with the above question. She said we can put it in excel and it will automatically put everything in. She inputed the formula =1/5r1 into the first cell (because a 5 is in the first spot and she needs it to be a 1). Then she said we can copy and past for the rest of the row. Well I know how to copy and paste but I don't know how she got the first row answer.

2. A= [2 0 0 1]

----------[0 1 0 0]

----------[0 0 -1 0]

----------[0 0 0 2]

Dont' have anything on this because I am totally confused.

Answer 1

The first row should be (1/5)[5  0  2  1  0  0] = [1  0  .4  .2  0  0], not

[1  0  .4  1/2  0  0].

Answer 2

 5 0  2 1 0 0

 2 2  1 0 1 0

-3 1 -1 0 0 1

1 0 2/5  1/5 0 0

0 2 1/5 -2/5 1 0

0 1 1/5  3/5 0 1

1 0 2/5 1/5 0 0

0 1  0   -1  1 -1

0 1 1/5 3/5 0 1

1 0 2/5 1/5 0 0

0 1  0   -1  1 -1

0 0 1/5 8/5 -1 2

1 0 0 -3  2 -4

0 1 0 -1  1 -1

0 0 1  8 -5 10

This link will show you how to compute an inverse in Excel: http://www.math.iupui.edu/~momran/m118/m... .

Note especially the instruction to press Shift-Ctrl-Enter.