DefinitionAn exact differential equation is an ordinary differential equation (ODE) for which the substituted form M(x,y)dx + N(x,y)dy = 0 is exact (meaning that it is a total differential). An exact differential equation has integrating factors so that it can be derived by the total differential of a function and can be integrated directly. In the physical sciences, exact differential equations are used to model a number of different activities, such as heat flow, flow of fluids, population growth, among otherthings. For Example,The given exact differential equation(2xy+y2)dx+(x2+2xy)dy=0 can be easily recognized as exact as here ∂y∂(2xy+y2)=∂x∂(x2+2xy), so we can rewrite this form as d(x2y+31y3)=0