Question 1008286
3r +5s + t =0
3r –s –3t = 4
-3r-4s-4t= -19 
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Subtract row 1 from row 2
Add row 1 to row 3
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3r +5s + t =0
0 –6s –4t = 4
0 + s -3t = -19
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Interchange rows 2 and 3 to get::
3r +5s + t =   0
0  + s -3t = -19
0  –6s –4t =   4
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Add 6 times row 2 to row 3 to get:
3r +5s + t =   0
0  + s -3t = -19
0  + 0 -22t = -110
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Solve row 3 to get: t = 5
Solve row 2 to get: s = 3*5-19 = -4
Solve row 1 to get: r = (-5*-4 -5)/3 = 5
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Cheers,
Stan H.
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