变量满足,则的最小值为_____. 答案:【答案】-2【解析】先作出不等式组对应的可行域,再利用数形结合分析求解.由题得不等式组对应的可行域如图所示,联立.因为,所以,当直线经过点C(2,-2)时,直线的纵截距最小,z最小.此时z最小值为2+2(-2)=-2.故答案为:-2Since 1939, numerous scientific studies have
been conducted to determine 1
smoking is a health
threat. The 2 of the 3
has been consistent
(constant) and indicates that there is a serious health risk. Research teams
have conducted studies that show 4
all reasonable doubt
that tobacco smoking, particularly cigarette smoking is 5 with
a 6 life
expectancy (time). Cigarette smoking is believed by most research workers in
this 7 to be an important 8
in the development of
cancer of the lungs and cancer of the throat and is believed to be related 9 cancer of other organs. Male cigarette smokers have a higher
death 10 from heart disease than non-smoking males. (Female smokers
are thought to be 11 affected because they do not breathe in
the smoke 12 deeply.) The 13
of physicians and
researchers consider these relationships proved 14
their satisfaction and
say, “Give 15 smoking, if you don't smoke don't start!”
Smoking does 16 to
the lungs. Smoking also affects the heart and blood vessels. Smokers also die
much more often 17
heart disease.
While all
tobacco smoking affects life expectancy and health, cigarette smoking appears
to have a much greater effect than cigar or pipe smoking. 18 , nicotine
consumption is not decreased by the latter forms, and current research
indicates a 19 relationship between all forms of smoking and cancer of the
mouth and throat. Filters and low tar tobacco are claimed to make smoking to
some 20 safer, but they can only marginally reduce, not eliminate the
threats.
1.
A. that B.
whether
C. what D.
which
2.
A. style B.
fashion
C. trend D.
drift
3.
A. matter B.
affair
C. exhibit D.
evidence
4.
A. to B.
in
C. beyond D.
for
5.
A. associated B.
joined
C. mixed D.
tied
6.
A. cutting B.
shortened
C. lessening D.
lengthened
7.
A. field B.
part
C. aspect D.
ground
8.
A. point B.
key
C. factor D.
step
9.
A. of B.
on
C. by D.
to
10.
A. rate B.
ratio
C. pace D.
speed
11.
A. mentally B.
less
C. directly D.
strongly
12.
A. far B.
such
C. so D.
still
13.
A. few B.
majority
C. minority D.
most
14.
A. to B.
for
C. with D.
of
15.
A. in B.
up
C. away D.
out
16.
A. harm B.
injury
C. wound D.
hurt
17.
A. in B.
from
C. with D.
by
18.
A. Moreover B.
Though
C. Therefore D.
However
19.
A. personal B.
intimate
C. causal D.
social
20.
A. area B.
length
C. size D.
extent