|x-1|+|y|=1
Th1:$\left \{ {{x-1=0} \atop {y=1}} \right.$ =>$\left \{ {{x=1} \atop {y=2}} \right.$
Th2: $\left \{ {{x-1=1} \atop {y=0}} \right.$ =>$\left \{ {{x=2} \atop {y=0}} \right.$
Th3:$\left \{ {{x-1=-1} \atop {y=0}} \right.$ =>$\left \{ {{x=0} \atop {y=0}} \right.$
Th4: :$\left \{ {{x-1=0} \atop {y=-1}} \right.$ =>$\left \{ {{x=1} \atop {y=-1}} \right.$
Vậy (x,y)∈{(1;2);(2;0)'(0;0)'(1;-1)