In this paper, we investigate the existence and uniqueness of solutions and Ulam's type stabilities including the well-known Ulam-Hyers stability and the newly extended Ulam-Hyers' conformable exponential stability for two classes of fractional differential equations with the conformable fractional derivative and the time delay. The Banach contraction principle, the technique of Picard operator, the Gronwall integral inequalities and generalized iterated integral inequality in the sense of conformable fractional integral are the main tools for deriving our main results. Finally, several illustrative examples will be presented to demonstrate our work.

In this work, a class of fractional delay differential equations with four-point boundary condition and p-Laplacian operator are discussed. Based on the Avery-Peterson theorem, the existence of at least triple positive solutions are derived. An simple example are given to show the validity of the conditions of our main theorem.