The feasible region for a LPP is shown in Fig. 12.10. Evaluate Z=4 x+y at each of the corner points of this region. Find the minimum value of \mathrm{Z}, if it exists.
The feasible region for a LPP is shown in Fig. 12.10. Evaluate Z=4 x+y at each of the corner points of this region. Find the minimum value of \mathrm{Z}, if it exists.

NCERT Exemplar Solutions Class 12 Mathematics Chapter 12 - 9

Solution:

It is given that: Z=4 x+y

In the figure given, \mathrm{ABC} is the feasible region which is open unbounded.

Here, we get

x+y=3\dots \dots(i)

and \quad x+2 y=4 \quad \ldots (ii)

On solving equations equation(i) and equation(ii), we obtain

x=2 and y=1

Therefore, the corner points are \mathrm{A}(4,0), \mathrm{B}(2,1) and \mathrm{C}(0,3)

On evaluating the value of Z, we get

The corner points

Z=4 x+y

Z=4(4)+(0)=16

    \[\begin{tabular}{|l} $\mathrm{B}(2,1)$ $\mathrm{C}(0,3)$ \end{tabular}\]

NCERT Exemplar Solutions Class 12 Mathematics Chapter 12 - 10

Now, the minimum value of \mathrm{Z} is 3 at (0,3) but as, the feasible region is open bounded so it can or can not be the minimum value of Z. As a result, in order to face such a situation, we usually draw a graph of 4 \mathrm{x}+\mathrm{y}<3 and check whether the resulting open half plane has no point in common with feasible region. Otherwise \mathrm{Z} will have no minimum value. Therefore, from the graph, it can be concluded that there is no common point with the feasible region.

Thus, the function \mathrm{Z} has the minimum value at (0,3)