ABSTRACT
The condition b1c2 – b2c1 ≠ 0 is assumed to hold. Multiplying the equations by appropriate constants and then adding together, one arrives
at two independent equations:
∂2U
∂t2 = a
∂2U
∂x2 + (b1c2 – b2c1)f (U ), U = b1u + c1w;
∂2W
∂t2 = a
∂2W
∂x2 – (b1c2 – b2c1)g(W ), W = b2u + c2w.
