Formulate the constraints which represent the above feasible region.

The boundary lines of the feasible region are: 1. Line through $A(1,1)$ and $B(3,3)$: equation is $y = x \Rightarrow x - y \le 0$ (or $y - x \ge 0$). 2. Line through $B(3,3)$ and $C(1,7)$: slope is $\frac{7-3}{1-3} = -2$, equation is $y - 3 = -2(x - 3) \Rightarrow 2x + y \le 9$. 3. Vertical line through $A(1,1)$ and $C(1,7)$: $x \ge 1$. 4. Non-negativity constraints: $x \ge 0, y \ge 0$. Therefore, the constraints representing the feasible region are: $2x + y \le 9$, $x - y \le 0$, $x \ge 1$, $x \ge 0, y \ge 0$.