问题 解答题
我们知道,分式和分数有着很多的相似点.小学里,把分子比分母小的分数叫做真分数.类似的,我们把分子的次数小于分母的次数的分式称为真分式,反之,称为假分式.对于任何一个假分式都可以化成整式与真分式的和的形式,如 
x+1
x-1
=
x-1+2
x-1
=
x-1
x-1
+
2
x-1
=1+
2
x-1

(1)下列分式中,属于真分式的是______
A、
x+2
x2-1
    B、
a+1
a-1
    C、
y2
y-1
   D、
b2+1
b2-1

(2)将假分式
t2+1
t+1
,化成整式和真分式的和的形式.
答案

(1)∵分子的次数小于分母的次数的分式称为真分式,反之,称为假分式.

真分式为A…(2分).

故答案为A;

(2)方法一:

t2+1
t+1
=
t2-1+2
t+1
=t-1+
2
t+1
…(4分)

方法二:

t2+1
t+1
=
t2+2t+1-2t
t+1
=t+1-
2t
t+1
=t+1-
2t+2-2
t+1
=t-1+
2
t+1
…(2分)

单项选择题
单项选择题

"In the long run," as John Maynard Keynes observed, "we are all dead. " True. But can the (1) run be elongated in a way that makes the long run (2) And if so, how, and at what cost People have dreamt of (3) since time immemorial. They have sought it since the first alchemist put an elixir of (4) on the same shopping list as a way to turn lead into gold. They have (5) about it in fiction, from Rider Haggard’s "She" to Frank Herbert’s "Dune". And now, with the growth of (6) knowledge that has marked the past few decades, a few researchers believe it might be within (7) .

To think about the question, it is important to understand why organisms-people (8) -age in the first place. People are like machines: they (9) That much is obvious. However, a machine can always be (10) A good mechanic with a stock of spare parts can keep it going (11) . Eventually, no part of the (12) may remain, but it still carries on, like Lincoln’s famous axe that had three new handles and two new blade.

The question, of course, is whether the machine is worth (13) . It is here that people and nature (14) . Or, to put it slightly (15) , two bits of nature disagree with each other. From the individual’s point of view, (16) is an imperative. You cannot reproduce unless you are alive. A fear of death is a sensible evolved response and, since (17) is a sure way of dying, it is no surprise that people want to stop it in its tracks. Moreover, even the appearance of ageing can be (18) . It (19) the range of potential sexual partners who find you attractive-since it is a sign that you are not going to be (20) all that long to help bring up baby-and thus, again, curbs your reproduction.

16()

A.living

B.survival

C.death

D.reproduction