(1)z represents the slope of the connecting line between D (-3,-1) and each point in the area, kAD = 3, kCD = 4/ 13,

So the range of z is [4/13,3].

(2) z = (x+ 1)2+(y+ 1)2+1where (x+1) 2 indicates that the points in the area are related to e (.

Therefore, the value range of z [6,26].