题干

将函数y=﹣2x的图象向下平移3个单位,所得图象对应的函数关系式为(   )

A:y=﹣2(x+3)

B:y=﹣2(x﹣3)

C:y=﹣2x+3

D:y=﹣2x﹣3

上一题 下一题 0.0难度 选择题 更新时间:2019-11-11 01:00:51

答案(点此获取答案解析)

D

同类题4

阅读理解。阅读下列四篇短文,从每小题后所给的A、B、C、D四个选项中,选出最佳选项。

    The Colonel(上校) asked Ashenden a good many questions and then suggested that he had particular qualifications for the Secret Service. Ashenden knew several European languages and the fact that he was a writer provided excellent cover: on the pretext(借口) that he was writing a book he could, without attracting attention, visit any neutral country.

    It was while they were discussing this point that the Colonel said, "You know you might get material that would be very useful to you in your work. I'll tell you an incident that occurred only recently. Very dramatic. A foreign government minister went down to a Mediterranean resort to recover from a cold and he had some very important documents with him that he kept in a dispatch case(公文箱). A day or two after he arrived, he picked up a beautiful blonde at some restaurant or other, and he got very friendly with her . He took her back to his hotel, and when he came to himself in the morning, the lady and the dispatch-case had disappeared. They had one or two drinks up in his room and his theory is that when his back was turned the woman slipped a drug in his glass.

    "Do you mean to say that happened the other day?" said Ashenden.

    "The week before last ."

    "Impossible," cried Ashenden. "Why! We've been putting that incident on the stage for sixty years, we've written it in a thousand novels. Do you mean to say that life has only just caught up with us?"

    "Well, I can guarantee the truth of the story." said the Colonel, "And believe me, the government has been put to no end of trouble by the loss of the documents."

    "Well sir, if you can't do better than that in the Secret Service," sighed Ashenden, " I'm afraid that as a source of inspiration to the writer of fiction, it's washout(失败)."

同类题5

为了从甲、乙、丙三种微生物获取高性能碱性淀粉酶,兴趣小组的同学在科研人员的帮助下,从上述三种微生物提取了淀粉酶提取液(提取液中酶浓度相同),进行了如下实验.

【实验步骤】:

(1)取四支试管,分别编号.

(2)按下表要求完成操作.并在表中各列的字母位置,填写相应试剂的体积量(mL).

 

试管1

试管2

试管3

试管4

蒸馏水

2

2

2

A

pH=8缓冲液

0.5

0.5

0.5

0.5

淀粉溶液

1

1

1

1

甲生物提取液

0.3

 

 

 

乙生物提取液

 

0.3

 

 

丙生物提取液

 

 

0.3

 

总体积

3.8

3.8

3.8

B

(3)将上述四支试管放入37℃的水浴,保温1小时.

(4)取出上述四支试管,冷却后滴入碘液.

(5)观察比较各支试管溶液颜色及其深浅.

【实验结果】(“+”表示颜色变化的深浅,“﹣”表示不变色):

 

试管1

试管2

试管3

试管4

颜色深浅程度

++

+

C

请回答下列问题:

(1)填写表中的数值:A为____ ,C的颜色深浅程度为____ (用“+”或“﹣”表示).该实验作为实验组的试管是____ ,设置对照实验的目的是____ 

(2)该实验的自变量是____,无关变量有____ (至少写出2种).

(3)除了用碘液检验淀粉的剩余量来判断实验结果外,还可以用____试剂来检测生成物.若用该试剂检验,还需要对试管____处理,才能据颜色变化深浅判断出实验结果.

(4)根据上述结果得出的实验结论是:不同来源的淀粉酶,虽然酶浓度相同,但活性不同.你认为造成实验中三种酶活性差异的根本原因是____