问题 解答题

阅读以下解题过程:

已知a,b,c为△ABC的三边,且满足a2c2-b2c2=a4-b4,试判断△ABC的形状.

错∵a2c2-b2c2=a4-b4…(1),

∴c2(a2-b2)=(a2-b2)(a2+b2)…(2),

∴c2=a2+b2…(3)

问:

(1)上述解题过程,从哪一步开始发现错误请写出该步的代号______.

(2)错误的原因是______.

(3)本题正确的结论是______.

答案

∵c2(a2-b2)=(a2-b2)(a2+b2)∴应有c2(a2-b2)-(a2-b2)(a2+b2)=0得到(a2-b2)[c2-(a2+b2)]=0,∴(a2-b2)=0或[c2-(a2+b2)]=0,即a=b或a2+b2=c2,∴根据等腰三角形得定义和勾股定理的逆定理,三角形为等腰三角形或直角三角形.故填③,不能确定a2-b2是否为0,等腰三角形或直角三角形.

阅读理解

阅读理解。

     Several days ago, a Beijing-based IT company fired about 400 people overnight. No one had expected

the job cuts, which broke with traditional ways of letting go of workers in China. Moreover, what was

special about this case was that the day before the 400 were fired, they all received from their boss a

gift-the book "Who Moved My Cheese?" The book-a bestseller in the US-is being used by men and women

to deal with changes in their lives and work. Some large organizations, including Coca-Cola, Kodak and

General Motors, ask their employees to read it to encourage them to be active towards changes. Cheese is

something related to everyone's livelihood-our jobs, the Industries we work in, relationships and love as well.

With China's official entry into the WTO, the whole nation will face more changes and challenges. So what

should we do once this "cheese" on which we are so dependent is moved? "Whatever challenges and

changes we meet, we should face up to them bravely", Jiang Hengwei, a civil servant said after reading the

book. Professor Zhang Yang in Renmin University of China agrees. "We should change our way of thinking.

The coming competitive foreign companies and products provide us with great chances to learn from them

and improve our own products to meet international standards and be more competitive." "With hard work

and wisdom, we will create a much larger and better piece of cheese." Zhang smiled confidently.

1. The whole passage is about _______.

A. people's opinions about a bestseller of the US

B. what people think about China's entry into the WTO

C. the change in people's attitude towards changes and challenges

D. how a book influences the Chinese

2. The company in Beijing gave each of the 400 fired workers a copy of "Who Moved My Cheese"

in order to _______.

A. be more competitive with foreign firms

B. find an excuse for their job cuts

C. let the workers make a living on their own

D. encourage the fired workers

3. The word "cheese" in the passage can refer to _______.

A. something we depend on for a living

B. a most important kind of food

C. change or challenge

D. way of life

4. From what Hengwei and Professor Zhang Yang said, we can know that _______.

A. they have different opinions on changes and challenges

B. people are not afraid of competition from foreign companies

C. the Chinese people are ready to face any changes and challenges

D. they are both greatly encouraged by the book

单项选择题