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问题 解答题
已知函数f(x)=
x+1-a
a-x
(a∈R且x≠a)，当f（x）的定义域为[a+
1
3
，a+
1
2
]时，求f（x）的值域．
答案

f(x)=

-(a-x)+1
a-x
=-1+
1
a-x
．

当a+

1
3
≤x≤a+
1
2
时，-a-
1
2
≤-x≤-a-
1
3
，-
1
2
≤a-x≤-
1
3
，-3≤
1
a-x
≤-2，

于是-4≤-1+

1
a-x
≤-3，

即f（x）值域为[-4，-3]．

填空题

下列数据是硝酸钾固体在不同温度时的溶解度。

温度/℃020406080
溶解度/g13.331.663.9110169
（1）硝酸钾溶液中的溶剂是          。

（2）20℃时，向100 g水中加入31.6 g硝酸钾，充分溶解后得到     （填“饱和”或“不饱和”）溶液。

（3）20℃时，向100 g水中加入40 g硝酸钾，若使硝酸钾完全溶解，可采用的方法是      。

（4）如图，小烧杯中盛放的是（2）中所得的硝酸钾溶液。若将少量的下列物质分别小心地加入到大烧杯的水中，不断搅拌，一定能够使小烧杯中有固体析出的是     （填字母）

A．冰     B．浓硫酸   C．硝酸铵    D．干冰   E．氢氧化钠   F．氧化钙 

（5）向一定量饱和的石灰水中加入少量的生石灰恢复到原温度，产生的现象是       ；其中改变的量是      。（提示：CaO+H2O→Ca(OH)2 ）

A．溶质的质量   B．溶剂的质量   C．溶液的质量    D．溶质的质量分数
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单项选择题

A long-term health study that followed a group of people who were age 35 in 1950 found that those whose weight increased by approximately half a kilogram or one pound per year after the age of 35 tended, on the whole, to live longer than those who maintained the weight they had at age 35. This finding seems at variance with other studies that have associated weight gain with a host of health problems that tend to lower life expectancy.
Which one of the following, if true, most helps to resolve the apparently conflicting findings ？（）

A．As people age, muscle and bone tissue tends to make up a smaller and smaller proportion of total body weight.

B．Individuals who reduce their cholesterol levels by losing weight can thereby also reduce their risk of dying from heart attacks or strokes.

C．Smokers, who tend to be leaner than nonsmokers, tend to have shorter life spans than nonsmokers.

D．The normal deterioration of the human immune system with age can be slowed down by a reduction in the number of calories consumed.

E．Diets that tend to lead to weight gain often contain not only excess fat but also unhealthful concentrations of sugar and sodium.
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