给定区域 $D$: $\left\{\begin{array}{c}x+4y⩾4\\ x+y⩽4\\ x⩾0\end{array}\right.$,令点集 $T=\left\{\overline{)\left(x_0,y_0\right)\in D}{x}_0,y_0\in Z,\left(x_0,y_0\right)是z=x+y在D\mathrm{上取得最大值或最小值的点}\right\}$,则 $T$中的点共确定条不同的直线.