若x、y∈R，且x+2y=5．则3x+9y的最小值是（） A．10 B．63 C．4

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问题选择题

若x、y∈R，且x+2y=5．则3^x+9^y的最小值是（　　）

A．10

B．6

C．4

D．18

答案

3x+9y=3x+32y≥2

3x+2y

=18

．当且仅当x=2y=

时取等号．

故选D．

阅读理解

阅读短文，判断下列句子正(T)误(F)。

Today the sun is sunny. We're going to go to the park on foot. There are lots of interesting things in the

park.Some people are rowing a dragon boat. Some people are doing Taijiquan. Some people are playing chess.

Two girls are playing the flute. We're going to go home by bus in the afternoon.

( ) 1. There are lots of interesting things in the zoo.

( ) 2. Two girls are rowing a dragon boat in the park.

( ) 3. Some people are doing Taijiquan.

( ) 4. Two boys are playing the flute.

( ) 5. We're going to go home on foot in the afternoon.

填空题

今年全球流行甲型H1N1流感，患上这一流感后第一症状就是发热，因此要用到体温计测量体温，如图所示是体温计和实验室常用温度计，请简要说出它们在构造或使用上的三个不同点。

不同点一：__________________________；

不同点二：__________________________；

不同点三：__________________________。