SOLUTION: solve the linear system by graphing 2x+y=-8 and -x+y=4 I know they intersect at -4. Is it 0 and -4 or -4 and 0

Algebra ->  Test -> SOLUTION: solve the linear system by graphing 2x+y=-8 and -x+y=4 I know they intersect at -4. Is it 0 and -4 or -4 and 0      Log On


   

Question 684259: solve the linear system by graphing
2x+y=-8 and -x+y=4 I know they intersect at -4. Is it 0 and -4 or -4 and 0
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

2x%2By=-8 and
-x%2By=4
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Solved by pluggable solver: Solve the System of Equations by Graphing



Start with the given system of equations:


2x%2By=-8

-x%2By=4





In order to graph these equations, we need to solve for y for each equation.




So let's solve for y on the first equation


2x%2By=-8 Start with the given equation



1y=-8-2x Subtract 2+x from both sides



1y=-2x-8 Rearrange the equation



y=%28-2x-8%29%2F%281%29 Divide both sides by 1



y=%28-2%2F1%29x%2B%28-8%29%2F%281%29 Break up the fraction



y=-2x-8 Reduce



Now lets graph y=-2x-8 (note: if you need help with graphing, check out this solver)



+graph%28+600%2C+600%2C+-10%2C+10%2C+-10%2C+10%2C+-2x-8%29+ Graph of y=-2x-8




So let's solve for y on the second equation


-x%2By=4 Start with the given equation



1y=4%2Bx Add +x to both sides



1y=%2Bx%2B4 Rearrange the equation



y=%28%2Bx%2B4%29%2F%281%29 Divide both sides by 1



y=%28%2B1%2F1%29x%2B%284%29%2F%281%29 Break up the fraction



y=x%2B4 Reduce





Now lets add the graph of y=x%2B4 to our first plot to get:


+graph%28+600%2C+600%2C+-10%2C+10%2C+-10%2C+10%2C+-2x-8%2Cx%2B4%29+ Graph of y=-2x-8(red) and y=x%2B4(green)


From the graph, we can see that the two lines intersect at the point (-4,0) (note: you might have to adjust the window to see the intersection)