**Answer to Where the 2nd Line Went**

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

Notice that if I eliminate the 1st equation, then we can't see the line. Looking more closely, we see that the problem is that we have limited the

values too much:

`> `
**implicitplot({x+y=2,x+y=4},x=-1..2,y=-1..5);
**