private static SquareMatrix <T> Add <T>(SymmetricMatrix <T> firstMatrix, SquareMatrix <T> secondMatrix) => Add(secondMatrix, firstMatrix);
private static SquareMatrix <T> Add <T>(DiagonalMatrix <T> lhs, SquareMatrix <T> rhs) => Add(rhs, lhs);
private static SquareMatrix <T> Add <T>(DiagonalMatrix <T> firstMatrix, SquareMatrix <T> secondMatrix) => Add(secondMatrix, firstMatrix);
private static SquareMatrix <T> Add <T>(SymmetricMatrix <T> lhs, SquareMatrix <T> rhs) => Add(rhs, lhs);