2x2-6x-7=0（配方法解）_爱下问搜题

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问题解答题

2x²-6x-7=0（配方法解）

答案

x²-3x-

7

2

=0，

x²-3x=

7

2

，

x²-3x+

9

4

=

23

4

，

(x-

3

2

)2=

23

4

，

x-

3

2

=±

23

2

，

x=

3

2

±

23

2

，

∴x₁=

3+

23

2

，x₂=

3-

23

2

．

完形填空

In the 13th century, Marco Polo travelled a long way to China. He was a famous Italian 31 During his stay in China, he saw many wonderful things. One of the things he 32 was that the Chinese used paper money. People in 33 countries didn’t use paper money until the 17th century. However,people in China began to use paper money in the 10th century. 34 was invented by a Chinese about 2 000 years ago. His name was Cai Lun. He then 35 these pieces of paper together and made them into a 36 .
Now paper mainly comes from trees. We use it every day. 37 we waste a lot of it. If we keep on doing so, people 38 cut down many more trees. Then there will not be any trees left. If there are no 39 , there will be no paper.
So how can we 40 paper? When we making notes,we can use 41 sides of each piece of paper. We can buy drinks in bottles instead of 42 in paper packets. We can also use cotton handkerchiefs ( 棉手帕) and not the paper ones.
43 we go shopping, we can use fewer paper bags. If the salesman gives us a paper bag, we can keep it and 44 it later. We can help to protect trees if we think 45 . We should to it now,before it is too late.

D．shouldn’t

小题9: A. books B. trees C, leaves D. factories

多项选择题

患者，男，28岁。被疑为疟疾，但第一次血涂片检查为阴性。为明确诊断可进行哪些检查（）

A.可反复做血涂片检查

B.行骨髓涂片检查

C.激发试验

D.免疫学诊断方法

E.基因诊断方法