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问题 问答题

设三阶矩阵


t为何值时，矩阵A，C相似说明理由．

答案

参考答案：

[*]
=(λ-2)(λ-3)(λ-1)，
则C有三个不同的特征值λ1=1，λ2=2，λ3=3，且存在可逆阵P，使得
[*]
[*]
=(λ-t)(λ-3)(λ-1)．
当t=2时，A有与C一样的三个不同的特征值，故有
Q-1AQ=A=P-1CP．
从而有(QP-1)-1A(QP-1)=C，即A～C．

完形填空

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It seems recently that more and more of my friends are facing some seemingly unbeatable challenges in their lives. Some have lost their jobs and some have __ 小题1:___ (fail) marriages. All too many have health problems.

I don’t know if it is desperation __小题2:___ causes them to turn to me for advice or whether they have come to value our friendship. But __小题3:___ is difficult to offer words of hope when all they feel is hopeless. They expect answers to get them back __小题4:___ their feet again.

I have often struggled with what to say,  ___小题5:___ (most) because I have faced many of the same challenges in my own life. I remember how empty I felt after someone cheerfully offered words like “Things will get better!”

Now , being thought of __小题6:___ a source of hope or a good example of what to do through printed words, I have even __小题7:___ (many) people contacting me.

So what do I say? “Begin again.”

It sounds too simple, __小题8:___ it is indeed the answer. All life __小题9:___(challenge) bring about an ending and the chance for __小题10:___(begin).
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单项选择题

寄生在脑组织内形成包裹而导致脑囊虫病的是猪带绦虫的（）

A.六钩蚴

B.节片

C.蚴虫和六钩蚴

D.囊尾蚴

E.虫卵
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