Question 304660
Solve the following by substitution: x + y = 0, 3x + 3y = 4. Are these equations independent, dependent or inconsistent?
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They're inconsistent.  Multiply the 1st eqn by 3:
--> 3x + 3y = 0
The 2nd says 3x + 3y = 4
If you graph them, they're parallel.  No intersection, no solution.
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What are the slopes of the above lines ?
The slopes are equal, = -1
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Change the second equation in problem 1 to 3x + 2y = 4. Solve by substitution. 
x + y = 0  --> y = -x
3x + 2y = 4
Sub for y
3x + 2(-x) = 4
x = 4
y = -4