Question 1156550
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for y=-3x+9 and y=-3x+3

and for y=-x-3y and y=x+1
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{{{graph(400,400,-5,10,-5,10,-3x+9,-3x+3)}}}
No intersection; two parallel lines





{{{graph(400,400,-3,3,-3,3,-x/4,x+1)}}}
Intersection is at {{{system(x=-4/5, and, y=1/5)}}}.