Definition: A differential equation of the form M(x ,y)+N(x ,y)=0, is called Exact if

¶ M/¶ y =¶ N/¶ x. There exists a solution F(x ,y) such that M(x ,y)=F _x

and N(x ,y)=F_y.

       Assignment:sec 1.13: odd problems: 1-13