Maximizing or Minimizing Objectives with Constraints in Linear Programming, Lecture notes of Operational Research

The concept of linear programming, which involves maximizing or minimizing an objective function using decision variables and constraints. The notation and format of the objective function and constraints, as well as the ability to recognize when a problem can be formulated as a linear programming model. The document also mentions the possibility of minimizing cost and dealing with greater than or equal constraints and equalities.

Typology: Lecture notes

2011/2012

Uploaded on 08/06/2012

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LINEAR PROGRAMMING PROBLEM
Let xi = decision variable for ith variable.
ci = profit or cost co-efficient of ith variable.
Z = function to be maximized or minimized.
Thus for n decision variables, the objective function is to maximize or minimize
Z = c1 x1 + c2 x2 + ... + cn xn
Let aij = co-efficient of the jth constraint and ith variable
bi = resource limitation for ith constraint
Thus the restrictions may be expressed in the general form
a11x1 + a12x2 + ... + a1nxn < b1
a21x1 + a22x2 + ... +a2nxn < b2
: : : :
am1x1 + am2x2 + ...+ amnxn < bm
and xi > 0 for all values of i from 1 to n
The same linear programming problem can be expressed in a more condensed form using summation
notation or matrix equation.
Maximize
1
n
ii
i
Z c x
Subject to
n
ij j
ji
ax
for all i = 1, 2, ..., m
and xj > 0 for all j = 1, 2, ..., n
or
Maximize Z = CX , subject to AX < B
where C is a row vector and X and B are column vectors. A is a co-efficient matrix of the order m x n.
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L

LINEAR PROGRAMMING PROBLEM

Let xi = decision variable for ith variable. ci = profit or cost co-efficient of ith variable. Z = function to be maximized or minimized.

Thus for n decision variables, the objective function is to maximize or minimize

Z = c 1 x 1 + c 2 x 2 + ... + cn xn

Let aij = co-efficient of the jth constraint and ith variable

bi = resource limitation for ith constraint

Thus the restrictions may be expressed in the general form

a 11 x 1 + a 12 x 2 + ... + a1nxn < b 1

a 21 x 1 + a 22 x 2 + ... +a2nxn < b 2

am1x 1 + am2x 2 + ...+ amnxn < bm

and xi > 0 for all values of i from 1 to n

The same linear programming problem can be expressed in a more condensed form using summation notation or matrix equation.

Maximize 1

n i i i

Z c x

Subject to

n ij j j i

a x

 for all i = 1, 2, ..., m

and xj > 0 for all j = 1, 2, ..., n

or

Maximize Z = CX , subject to AX < B

where C is a row vector and X and B are column vectors. A is a co-efficient matrix of the order m x n.

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The linear programming problem may have an objective function to minimize cost also.

The inequalities may be "greater than or equal" instead of "less than or equal". Further in some

cases, the restrictions involve "equalities".

The successful application of linear programming is the ability to recognize that the problem can be formulated as a linear programming model.

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