public static Matrix multiply(Matrix x, Matrix y)
	{
		if (x.col != y.row)
			return null;
		Double[][] mat = new Double[x.row][y.col];
		for (int i = 0; i < x.row; i++)
		{
			for (int j = 0;  j < y.col; j++)
			{
				Double sum = 0.0;
				for (int k = 0; k < x.col; k++)
				{
					sum += x.matrix[i][k] * y.matrix[k][j];
				}
				mat[i][j] = sum;
			}
		}
		return new Matrix(mat);
		
	}