SOLUTION: Solve the system x+y=9 and 4x+y=9

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Question 995318: Solve the system x+y=9 and 4x+y=9
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

x%2By=9...eq.1
4x%2By=9...eq.2
----------------------subtract eq.1 from eq.2
4x%2By-%28x%2By%29=9-9
4x%2Bcross%28y%29-x-cross%28y%29=0
3x=0
highlight%28x=0%29
go to eq.1, plug in 0 for x
x%2By=9...eq.1
0%2By=9
highlight%28y=9%29
so, these two lines intersecting each other in one point, (0,9)

+graph%28+600%2C+600%2C+-10%2C+10%2C+-10%2C+10%2C+-x%2B9%2C-4x%2B9%29+