Question 138333
Solve each system of equations using matrices (row operations). 
Problem 49:
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Here's what I've tried:
Original augmented matrix:
[1 -2  3   7]
[2  1  1   4]
[-3 2 -2 -10] 
------------------------
*R[3]=r[1]+r[3]
[ 1 -2 3  7]
[ 2  1 1  4]
[-2  0 1 -3]
-------------------------
*R[2]=-2r[1]+r[2]
*R[3]=2r[1]+r[3]
[1 -2 3 7]
[0 5 -5 -10]
[0 -4 7 11] 
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*R[2]=(1/5)r[2]
*R[3]=-2r[1]+r[3]
[1 -2 3 7]
[0 1 -1 -2]
[0 0 1 -3] 
You made an error in forming R[3}
You should leave r(1)alone and work r(2) against r(3)
I would suggest you not try to do 2 steps in one transformation of the matrix.

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Cheers,
Stan H.






*R[1]=2r[2]+r[1]
[1 0 1 3]
[0 1 -1 -2]
[0 0 1 -3] 
*R[1]=-1r[3]+r[1]
[1 0 0 6]
[0 1 -1 -2]
[0 0 1 -3] 
*R[2]=r[3]+r[2]
[1 0 0 6]
[0 1 0 -5]
[0 0 1 -3] 
Therefore, I assume that the answer is x=6, y=-5, z=-3
BUT it's not. The answer is actually x=2, y=-1, z=1
When I input the matrix into my TI 84 Plus, I get
[1 0 0 2]
[0 1 0 -1]
[0 0 1 1]
which is the correct answer. 
So, I know the start, I know the end, but I'm having trouble with the innards. Any suggestions? Thanks in advance for your help!