Question 437306
x-3y=9
x+3y= -3

solve equation by graphing 
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x-3y=9 --> x = 3y + 9
x+3y= -3 --> x = -3y - 3
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The graphs are straight lines, so 2 points are needed
x = 3y + 9
Pick 2 values for y and find x
y = 0, x = 9 --> (9,0)
y = -3, x = 0 --> (0,-3)
Plot those 2 points and draw a line thru them.
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Do the same for the other equation.
Where the 2 lines intersect is the x & y values that fit both equations.
That's the solution to the system.