Question 1025532
2x-3y-9z=-5
 x+3z=5
 -3x+y-4z=-10 
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The 2nd eqn has no y term, so eliminate y using the 1st and 3rd eqns.
2x-3y-9z=-5
-3x+y-4z=-10 times 3 --> -9x+3y-12z = -30
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2x -3y-9z=-5
-9x+3y-12z = -30
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-7x - 21z = -35
Divide by -7
x + 3z = 5
That's the same as eqn 2 --> dependent, no unique solution
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 (b) if your answer is dependent in (a), find the complete solution. Write x
 and y as functions of z.
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x = 5 - 3z
y = 5 - 5z