The constant variation formulae for singular fractional differential systems with delay

This paper considers the Caputo singular fractional differential systems with delay, and the Riemann–Liouville singular fractional differential systems with delay. A new function α−δα−δ is defined. By the D−D−inverse matrix and α−δα−δ function, two fundamental solutions are given. The constant variation formulae for singular fractional differential systems with delay are obtained.