Write a function that takes as an argument a two-dimensional array with 9 lines and 9 columns (with integer elements), and verifies if the matrix contains a valid Sudoku solution.

This isn't much "help". This is just saying: Make me a sudoku solver. We can give you a few hints but no one is going to make a sudoku solver just because you posted it here...
If your going to ask for something, please ask in a correct manner.