Which of the following is an exact differential equation?
(2xy)dx+(x2+1)dy=0(2xy)dx + (x^2+1)dy = 0(2xy)dx+(x2+1)dy=0
ydx+xdy=0y dx + x dy = 0ydx+xdy=0
2xdx+3ydy=02x dx + 3y dy = 02xdx+3ydy=0
All of the above.