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Graphical Method

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Graphical Method

Graphical Method
① Max Z = 6x1 + 8x2
Sub . to
5x1 + 10x2 ≤ 60
4x1 + 4x2 ≤ 40
x1, x2 ≥ 0
Find out the boundary values of x1 & x2

I. 5x1 + 10x2 = 60
x1 = 0 ; x 2 = 6
x1 = 12 ; x2 = 0

II. 4x1 + 4x2 = 40


x1 = 0 ; x2 = 10
x1 = 10 ; x2 = 0
x2 Scale
15 1 cm = 5 units
II

10 O - (0,0)
(0,6) C
I Solution Region A - (10,0)
B - (8, 2)
5 B (8,2) C - (0, 6)

A
0 5 15 x1
(10,0)
(0,0)
Max Z = 6x1 + 8x2

Substitute O, A, B & C in obj. function,


Z (0) = 0
Z (A) = 60
Z (B) = 64
Z (C) = 48

• Optimal solution, Z max = 64


x1 = 8 & x2 = 2
Graphical Method
2) Find the min. of the function, z = 2x – y subject to the constraints :

x+y≤5
x + 2y ≥ 8
x, y ≥ 0

I. x + y =5
x=0;y=5
x=5;y=0

II. x + 2y = 8
x= 0; y=4
x=8; y= 0
A (0, 4) ; Z = - 4
y
B (2,3) ; Z = 1
C
x+y=5 C (0,5) ; Z = - 5
5
• Opt. soln. Z min = - 5

4 x=0
A
B
3 x + 2y = 8 y=5

1 2 3 4 5 6 7 8 9 x
0
Graphical Method
3) Max. z = x1 + x2
Sub. to
x1 + x2 ≤ 1
-3x1+ x2 ≥ 3
x1, x2 ≥ 0

I. x1 + x2=1
x1 = 0 ; x2 = 1
x1 = 1 ; x2 = 0

II. -3x1 + x2 = 3
x1 = 0 ; x2 = 3
x1 = -1 ; x2 = 0
There is no point (x1,x2) that satisfies both the
x2 constraints simultaneously.

• So, it is having an unbounded or infeasible


II solution.
4

0 1 2 3 x1
-1
I

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