Conditional correctness of the initial-boundary value problem for a system of high-order mixed-type equations

We investigate an ill-posed boundary value problem for a differential equation and a system of high-order partial differential equations with one line of degeneration. An a priori estimate of the solution is obtained by the method of logarithmic convexity. Theorems of uniqueness and conditional stability of the solution on the set of well-posedness of the problem under study are proved.