A DE deduced from the direction field

[ehabmozart]

Homework Statement

Which of the following dierential equations corresponds to the direction eld
shown below?

1) y'=x+y
2) y'=xy-1
3) y'=1-xy
4) y'-xy
5) y'=x-y

Homework Equations

The Attempt at a Solution

I have no idea how can this be done. I mean I used to deduce the DE from the direction field only when the equilibrium solution was HORIZONTAL.. Now, I am confused! Anyone who would help, I would appreciate it.

 

[haruspex]

For what (x,y) is y'=0 in the picture?