SOLUTION: y=2x x-y=4 solve by substituition

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Question 150380: y=2x
x-y=4
solve by substituition
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Start with the given system of equations:


system%28y=2x%2Cx-y=4%29


x-y=4 Start with the second equation.


x-2x=4 Plug in y=2x


-x=4 Combine like terms on the left side.


x=%284%29%2F%28-1%29 Divide both sides by -1 to isolate x.


x=-4 Reduce.


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Since we know that x=-4, we can use this to find y.


y=2x Go back to the first equation.


y=2%28-4%29 Plug in x=-4.


y=-8 Evaluate the right side.


So the answer is x=-4 and y=-8.


This means that the system is consistent and independent.


Notice when we graph the equations, we see that they intersect at . So this visually verifies our answer.


Graph of y=2x (red) and x-y=4 (green)