“…Note that on questions of existence, uniqueness and blow-up of solutions of initial, mixed, nonlocal and other problems posed for nonlinear hyperbolic type equations there are devoted a number of papers (see, e.g. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]). In linear case, i. e. when g(x, t, u) = g(x, t), problem (1.1), (1.2), as it is known, is wellposed and a global solvability takes place in corresponding function spaces Multiplying the both sides of equality (2.5) by u nt and integrating the received in domain D τ := (x, t) ∈ D T : 0 < t < τ , 0 < τ ≤ T we have…”