The Student Room Group

LP Graph Extreme Points & Feasible Region

can anyone help me identify the extreme point and the feasbile region for this linear programming problem graph?

thanks
Original post by JoeyA95
...


You really need to label your graph as that will help you out. You have sketched the lines but you haven't indicated which region you are interested in. (You need to indicate which side of the line actually gives solutions to the inequality).

Once you have done that if the problem has a solution the feasible region (the set of all points that satisfy all inequalities) will be clear as it will be the only region that where all the inequalities are met and this should be obvious from the diagram.

The extreme points are just the intersections of the lines you have drawn and if a solution exists to the LP problem then it will always lie on an extreme point.

So just use the equations of each line to find where they intersect (on the edge of the feasible region) and plug the intersection co-ordinates into whatever equation you want to max or min and see which is the solution.

Hope that helps.
Reply 2
Original post by poorform
You really need to label your graph as that will help you out. You have sketched the lines but you haven't indicated which region you are interested in. (You need to indicate which side of the line actually gives solutions to the inequality).

Once you have done that if the problem has a solution the feasible region (the set of all points that satisfy all inequalities) will be clear as it will be the only region that where all the inequalities are met and this should be obvious from the diagram.

The extreme points are just the intersections of the lines you have drawn and if a solution exists to the LP problem then it will always lie on an extreme point.

So just use the equations of each line to find where they intersect (on the edge of the feasible region) and plug the intersection co-ordinates into whatever equation you want to max or min and see which is the solution.

Hope that helps.


so would this be correct?
Original post by JoeyA95
.


Yes.

Now:

1)sketch the feasible region.
2)determine the coordinates of the edges of the feasible reason using the equations of the lines.

3) see which is optimal solution
Reply 4
Original post by poorform
Yes.

Now:

1)sketch the feasible region.
2)determine the coordinates of the edges of the feasible reason using the equations of the lines.

3) see which is optimal solution


so theres only 3 extreme points?

wouldnt there be one at (9,45)?
Original post by JoeyA95
so theres only 3 extreme points?

wouldnt there be one at (9,45)?


That is not feasible since x_1=9 is not more than 20. So it can't possibly be a solution and hence we are not interested in it.

The optimal solution to the LP is ALWAYS a extreme point of the feasible reason.

So just shade in the feasible region on the sketch and look at the corners of the shaded region :smile:

Quick Reply

Latest