A.恒为正数且有最小值3 B.恒为正数且有最小值1
C.恒为非负数且有最小值0 D.恒为非负数且无最小值
解析:
=x2+2(y+1)x+(y+1)2+y2+2y+4
=[x+(y+1)]2+(y+1)2+3≥
答案: