syms z

% Given z-transforms
F_a = z/(z+0.5)
F_b = z^2/(z-0.8)^2
F_c = z/((z+0.3)*(z+0.6)^2)

% Inverse z-transforms
f_a = iztrans(F_a)
f_b = iztrans(F_b)
f_c = simplify(iztrans(F_c))