Show that the minimum of $Z$ occurs at more than two points.
Maximize $Z = x + y$,subject to $x - y \leq -1$,$-x + y \leq 0$,$x, y \geq 0$.

(N/A) The given constraints are:
$1) x - y \leq -1 \implies y \geq x + 1$
$2) -x + y \leq 0 \implies y \leq x$
$3) x \geq 0, y \geq 0$
Analyzing the constraints:
Constraint $1$ requires $y$ to be at least $x + 1$.
Constraint $2$ requires $y$ to be at most $x$.
These two inequalities,$y \geq x + 1$ and $y \leq x$,are contradictory because $x + 1$ is always greater than $x$.
Therefore,there is no point $(x, y)$ that satisfies both conditions simultaneously.
Since there is no feasible region,the objective function $Z = x + y$ has no maximum or minimum value.