Consider the equation x + y = 5.
It passes through the points (0, 5) and
(5, 0). The line x + y = 5 is represented by AB.
Consider the inequality x + y < 5.
Put x = 0, y = 0
0 + 0 = 0 < 5, which is true. So, the origin O
lies in the plane x + y < 5
∴ Shaded region represents the inequality
x + y < 5.