[C++] Adding a Matrix with the multiplication of two other Matrix

Hello there guys.

I've a problem here.

I've a class with the operators =, + and * implemented.

Those operators are working well. The issue is related with a matrix equation.

What I need to do is:

[3x1](k+1) = [3x1] + [3x3] * [3x1](k) , Where those matrix are type Matrix.

A need that the matrix [3x1] holds the values from the result of that equation. This is a iterative method that I'm implementing.

Does anyone can help me out here?