In a normal curse of ordinary differential equations, it is common to find difficulties for the students to assimilate formal concepts of mathematics, in particular to solve an exact differential equation, in which they use the traditional method where they have to calculate at least two integrals that are a line integral in the real sense. This procedure is constructive but the exercises that the teacher usually proposed to the students are for memorize the algorithm and not for manipulate with a mathematical basis. As a consequence of this some students obtain correct solutions but they do not obtain maturity in the arguments behind the method as a students of engineering or science.