For the equation M(x,y)dx+N(x,y)dy=0M(x,y)dx + N(x,y)dy = 0M(x,y)dx+N(x,y)dy=0, what condition must hold for it to be exact?
∂M∂y=∂N∂x\frac{\partial M}{\partial y} = \frac{\partial N}{\partial x}∂y∂M=∂x∂N
∂M∂x=∂N∂y\frac{\partial M}{\partial x} = \frac{\partial N}{\partial y}∂x∂M=∂y∂N
M=NM = NM=N
∂M∂y+∂N∂x=0\frac{\partial M}{\partial y} + \frac{\partial N}{\partial x} = 0∂y∂M+∂x∂N=0