Which of these differential equations is NOT seperable?

Question

dy/dy=x+y

 

dy/dy=xy

 

dy/dy=x/y

 

dy/dy=2^xy

Answer 1

If dy/dx = xy, then (1/y)dy = xdx  (separable)

 

If dy/dx = x/y, then ydy = xdx (separable)

 

If dy/dx = 2^x/y, then ydy = 2^xdx (separable)

 

dy/dx = x+y is not separable