Problem by calculating the determinant of a nXn Matrix using symbolic elements

Hi everybody, im facing a problem, when i try to calculate 3X3 4X4 5X5 determinants with relatively long elements with symbolic terms using syms. The program gives a result which is not the correct one. Can anybody help me?

[Ahmed A. Selman]

An example of the code you tried, and the shape of one of these matrices, might help people willing to help you.