It is shown that the solutions to
the abstract differential equation u′ = −(A + B)u, u(0) = x ∈ X, where X is a
Banach space, −A is a linear analytic semigroup generator, and B is Lipschitz
continuous from the domain of a fractional power of A to X, have the exponential
representation u(t) =limn→∞(I + t∕n(A + B))−nx.