Abstract. This paper contains the application of the Finite Difference Method in the two-dimensional Fourier equation using Robin's boundary condition (the third boundary condition).

Abstract. In the article the next nontrivial example of non-Keller mapping having two zeros at infinity is analyzed. The rare mapping of two complex variables having two zeros at infinity is considered. In the article it has been proved that if the Jacobian of the considered mapping is constant, then it is zero.

Abstract. In the paper a nontrivial example of non-Keller mapping is considered. It is shown that the Jacobian of rare mapping, having one zero at infinity, being constant must vanish.

Abstract. In the paper the method of calculating of the determinants of block matrices is presented. The three-band matrices are considered, both in the particular case (3D) as well as in the general case.