多项式x2+y2-6x+8y+7的最小值为 ______.
原式=(x-3)2+(y+4)2-18,
当两完全平方式都取0时原式取得最小值=-18.
故答案为:-18.
____ is the first thing to consider when customers buy certain goods. [ ]
A. Reward
B. Quality
C. Value
D. Quantity
由石膏、麦冬、知母、牛膝、熟地黄组成的方剂是
A.麦门冬汤
B.养阴清肺汤
C.玉液荡
D.益胃汤
E.玉女煎