  In this paper, we establish blow-up rates for higher-order semilinear
parabolic equations with nonlocal in time nonlinearity with no positive
assumption on the solution. We also give Liouville-type theorem for
higher-order semilinear parabolic equation with infinite memory nonlinear term
which plays the main tools to prove our blow-up rate result. Finally, we study
the well-posedness of mild solutions.
