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【多选题】
数字滤波器的主要技术指标A.
通带截止频率
B.
阻带截止频率
C.
通带
D.
阻带
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举一反三
【简答题】Why doesn’t the unemployment rate ever reach zero? Economists, who generally believe that supply tends to meet demand, have long thought about this question. Even in good times, i.e. not now, there ar...
【单选题】Because it is difficult for economists to use experiments to generate data, they generally must
A.
do without dat
B.
substitute assumptions for data when data are unavailable.
C.
rely upon hypothetical data that were previously concocted by other economists.
D.
use whatever data the world gives them.
【简答题】已知n阶矩阵A满足A^2+2A-3I=O(这里,I是单位矩阵,O是零矩阵),则A的逆矩阵A^(-1)= ,(A+2I)^(-1)= ,(A+4I)^(-1)= . (答案为分数时,请在英文下用类似-3A/7的形式表示,负号用短的,中间不要写乘号)
【判断题】Economists generally believe that, although there may be advantages to society from ticket-scalping, the costs to society of this activity outweigh the benefits.
A.
正确
B.
错误
【单选题】Economists have generally found that economic growth rates have a close relation to:
A.
openness to trade
B.
education
C.
communications infrastructure
D.
all of these
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