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二次函数y=ax2+bx+c的值永远为负值的条件是a______0，b2-4ac______0．

答案

因为二次函数y=ax2+bx+c的值永远为负值，

所以函数图象的开口向下，所以a＜0．

此外，函数与x轴没有交点，所以b2-4ac＜0，

所以二次函数y=ax2+bx+c的值永远为负值的条件是a＜0，b2-4ac＜0．

填空题
根据短文内容，从方框中选择适当的词并用其正确形式填空，使短文内容完整。并将答案写在答题卡的相应位置上。（每个词只能用）
happy , different,  know,  both,  sad, friend, one, picture ,they, although
Bella and Fiona were classmates last year. But this year they are in 小题1:__________ classes. Bella is in Class A and Fiona is in Class B. On the ____小题2:___________day of this term, Bella looked around Class A. She小题3:_______few of the children. She was very 小题4:________ there. So she missed Fiona very much. In the art class, Bella sat alone in the classroom. She started painting a summer 小题5:__________. Then a child named John came and sat next to her. John told Bella about his summer vacation.小题6: ___________ both painted pretty summer pictures. Bella started feeling better. At the end of the art class they became good 小题7:__________. On that day, the same thing 小题8:_________ to  Fiona, too.
Bella’s father drove to their school to pick them up in the evening. Fiona and Bella were very happy to see each other. “小题9:_________ we are not in the same classroom, we can still see each other,” Bella said.
Bella and Fiona talked and laughed on the way home. They 小题10:_______ made new friends at school. But they wanted to keep their old friendship, too. 
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多项选择题

下列哪些治疗措施可减轻慢性心力衰竭患者的心脏负担

A．心身休息

B．吸氧

C．使用洋地黄类药物

D．使用扩血管药物

E．使用利尿剂
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