- Thread starter
- #1

- Thread starter suvadip
- Start date

- Thread starter
- #1

- Apr 14, 2013

- 4,119

Is there maybe a constraint, where b is negative? I mean for example $ -4x_1+2x_2 \leq -4$ ?In a LPP all the constraints are given as 'less than equal to' type. But it was asked to solve the LPP by Charnes Big M method. Is the question wrong?

According to me, we have to apply simplex method to solve it. There is no scope tp introduce M.

- Admin
- #3

- Mar 5, 2012

- 8,864

The Big M method is a generalization that allows for 'greater than or equal to' constraints.In a LPP all the constraints are given as 'less than equal to' type. But it was asked to solve the LPP by Charnes Big M method. Is the question wrong?

According to me, we have to apply simplex method to solve it. There is no scope tp introduce M.

The simplex method also solves those.

- Thread starter
- #4

Is there maybe a constraint, where b is negative? I mean for example $ -4x_1+2x_2 \leq -4$ ?

No, the LPP was

Max z=2x+3y

subject to

x+y<=8

x+2y<=5

2x+y<=8

x,y>=0

Can it be solved by Big M method?

- Admin
- #5

- Mar 5, 2012

- 8,864

No need. The regular simplex method works for this.No, the LPP was

Max z=2x+3y

subject to

x+y<=8

x+2y<=5

2x+y<=8

x,y>=0

Can it be solved by Big M method?

The only 'greater than' constraints are the non-negativity constraints, which are a standard part of the simplex method.

- Jan 31, 2012

- 253

- Thread starter
- #7

Actually I need a answer of type 'it can not be solved by Big M method' or 'it can be solved by Big M method'. The question was set in a university exam and it was clearly instructed to solve it by Big M method.No need. The regular simplex method works for this.

The only 'greater than' constraints are the non-negativity constraints, which are a standard part of the simplex method.

- Admin
- #8

- Mar 5, 2012

- 8,864

Then the answer is yes, it can be solved by the Big M method.Actually I need a answer of type 'it can not be solved by Big M method' or 'it can be solved by Big M method'. The question was set in a university exam and it was clearly instructed to solve it by Big M method.

- Thread starter
- #9

Then the answer is yes, it can be solved by the Big M method.

How? I guess the way may be like this:

let a constraint is x1+2x2<=5

Introducing slack variable x3 we can write

x1+2x2+x3=5

As we are bound to solve by Big M method, we can now introduce artificial variable x4 to get

x1+2x2+x3+x4=5

Am I right?

- Admin
- #10

- Mar 5, 2012

- 8,864

Correct.How? I guess the way may be like this:

let a constraint is x1+2x2<=5

Introducing slack variable x3 we can write

x1+2x2+x3=5

Huh? You already introduced x3 for the slack.As we are bound to solve by Big M method, we can now introduce artificial variable x4 to get

x1+2x2+x3+x4=5

Am I right?

No need to introduce x4 here??