Sketch the graph of the system
\left\{\begin{aligned}x+y & \leq 4 \\2 x-y & \leq 4 \\x & \geq 0 \\y & \geq 0\end{aligned}\right.The first two inequalities are the same as those considered in Example 3, and hence the points on the graph of the system must lie within the purple region shown in Figure 6. In addition, the third and fourth inequalities in the system tell us that the points must lie in the first quadrant or on its boundaries. This gives us the region shown in Figure 7.