四变元非齐次超双曲型方程的特征问题

The characteristic problem of nonhomogenenous ultrahyperbolic equation of four variates

利用

The existence and uniquenessof characteristic solution of the equation∑2 i=1 Uxixi- ∑2 j=1 Uyjyj+ C2 U = f( x1,x2 ,y1,y2 ) are proved by means of Fourier serier.Here C is a arbitary real number.