JAMB - Mathematics (2006 - No. 35)
The solution set of the shaded area above is
y ≥ 0, y ≥ x and y + x ≤ 4
y ≤ x, y + x ≤ 4
y + x ≥ 4, y ≤ x
y ≤ x, y + x ≤ 4 and y ≥ 0
Explicaţie
y = x implies y ≤ x
y + x = 4 implies y = 4 – x
∴y = 4 – x
∴y ≤ x, y + x ≤ 4 and y ≥ 0