Stuck on step 2 Inverse of Matrix Q

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Rohan

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Nov 29, 2006
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Is there anyone that could give me a dig out with this I am stuck on step 2

Here follows the problem :

1) Use the Gaussian elimination to find the inverse of the matrix Q

Q = matrix([[1, 2, 1], [-3, -4, 1], [4, 6, 4]])

using step1: Q3 - 3Q1 = I get the following

Q = matrix([[1, 2, 1], [0, 10, -2], [4, 6, 4]])

This is where I am stuck and I have the question about, (Question ??) in Q_31 how do I get the first value 0 ? I can not use the formula Q3 + Q1 because that would give me [5, 8, 5]
What is my pivotal equation ? or next pivot point to solve this ? :p

Eliz .... if you are out there I am sending a S.O.S to you now
 
[1 2 1] , [-3-4 1] , [4 6 4]
multiply first row by 3 and add to second
multiply first row by -4 and add to third

[1 2 1] , [0 2 4] , [0 -2 0]
multiply second row by -1 and add to first row
multiply second row by 1 and add to third

[1 0 -3] , [0 2 4 ], [0 0 4]
multiply fourth row by 3/4 and add to first
multiply fourth row by -1 and add to second

[1 0 0 ] , [0 2 0] , [0 0 4]
divide second row by 2
divide third row by 4

[1 0 0 ], [0 1 0 ] , [ 0 0 1] unit matrix

Do the above steps to a unit matrix and you will obtain the inverse matrix

please check for errors
Arthur
 
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