CHIKOUCHE, ImaneARIOUA, Yasine: supervisor2024-07-032024-07-032024-06https://dspace.univ-msila.dz/handle/123456789/43148This work studies the existence and uniqueness of solutions for a class of non-linear fractional differential equations and their system via the ψfractional derivatives with boundary values. The arguments for the study are based upon the BANACH contraction principle, SCHAEFER fixed point theorem. Moreover, some examples are shown to appear the strength of our significant result.enΨ-fractional differential equationsfixed pointn nonlinear ψ -fractional differential equationsexistenceuniquenessψ- fractional operatora system of differential equationsThesis