On the first order differantial equations and inequalities

In this thesis, firstly, history of fuzzy logic and its areas of usage in daily life mentioned and theory of fuzzy sets are touched on. Also, a literature research is done and consequently, a compilation is made about this matters. Fuzzy Analysis is spoken and a notions like fuzzy integral and Hukuhara differentiability, Hukuhara derivative, Seikkala derivative are mentioned. In this study, first order differential equations, their solutions, first order fuzzy differential inequalities are explained. Essentially, in this thesis, upper and lower solutions of first order differential equations are investigated and some comparison results are proved via method of upper and lower solutions.