How many decision variables can be used in graphical method and why?

How many decision variables can be used in graphical method and why? The graphical method of solving a linear programming problem can be used when there are only two decision variables. If the problem has three or more variables, the graphical method is not suitable.

The graphical method of solving a linear programming problem can be used when there are only two decision variables. If the problem has three or more variables, the graphical method is not suitable.