x + y = 2 x + y = 4

> implicitplot({x+y=2,x+y=4},x=-1..2,y=-1..2);

[Maple Plot]

Where did the 2nd line go? We know that there are no solutions to this linear system, so the 2nd line cannot be on top of the first line, since this would give us infinitely many solutions.

Answer to Where the 2nd Line Went