Let Z=3x+9y....(1)
Converting inequalities to equalities
x + 3y = 60
Points are (0,20),(60,0)
x+y=10
Points are (0,10),(10,0)
x - y = 0
Points are (0,0),(10,10),(20,20)
Plot the graph for the set of points
The graph shows the bounded feasible region. ABCD, with corner points A=(10,0),B=(5,5),C=(15,15) and D=(0,20)
To find maximum and minimum
Corner point Z = 3x + 9y
A = (0,10) 90
B = (5,5) 60
C = (15,15) 180
D = (0,20) 180
From the graph maximum value of X occurs at two corner points C(15,5) and D(0,20) with value 180 and minimum occurs at point B(5,5) with value 60.