In: Advanced Math
Find a basis of U = span {(1,1,2,3), (2,4,1,0), (1,5,-4,-9)}

| Row Operation 1:  | 
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add -1 times the 1st row to the 2nd row | 
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| Row Operation 2:  | 
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add -2 times the 1st row to the 3rd row | 
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| Row Operation 3:  | 
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add -3 times the 1st row to the 4th row | 
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| Row Operation 4:  | 
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multiply the 2nd row by 1/2 | 
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| Row Operation 5:  | 
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add 3 times the 2nd row to the 3rd row | 
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| Row Operation 6:  | 
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add 6 times the 2nd row to the 4th row | 
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| Row Operation 7:  | 
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add -2 times the 2nd row to the 1st row | 
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