Which of these systems is inconsistent?
x+y=1,x−y=1x+y=1, x-y=1x+y=1,x−y=1
x+y=1,2x+2y=2x+y=1, 2x+2y=2x+y=1,2x+2y=2
x+y=1,x+y=2x+y=1, x+y=2x+y=1,x+y=2
x=0,y=0x=0, y=0x=0,y=0