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【单选题】
欠阻尼系统的有阻振荡频率ωd、无阻尼固有频率ωn和谐振频率ωr比较( )。A.
ωr>ωd >ωn
B.
ωr>ωn >ωd
C.
ωn >ωr>ωd
D.
ωn >ωd>ωr
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皮皮学刷刷变学霸
举一反三
【判断题】In the U.S., assignments are felt to be given added weight by the passage of time.
A.
正确
B.
错误
【简答题】（3x﹣2y﹣5）（3x+2y﹣5）﹣2x（6x+y）﹣（3x﹣y）（﹣y﹣x）
【简答题】Given x,y,z∈R+ ,and 3x=4y=6z .Then write 3x, 4y, and 6z in order from least to greatest as ___.
【简答题】若x 2 ﹣y 2 =48，x+y=6，则3x﹣3y= _________ ．
【简答题】已知（3x﹣y+2） 2 +|x+y+6|=0，则xy=（ ）。
【单选题】______ , he went to bed.
A.
A great weight taking off his mind
B.
With a great weight taking off his mind
C.
A great weight being taken off his mind
D.
With a great weight being taken off his mind
【简答题】已知实数x、y、z满足3 x ＝4 y ＝6 z ＞1. (1)求证： ＋ ＝ ； (2)试比较3x、4y、6z的大小．
【单选题】A variety o{ extracurricular activities are added in American schools______.
A.
to help students climb the education ladder
B.
to enrich students' dull life at school
C.
to help students become more successful in later life
D.
to extend college education down into elementary schools
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【简答题】Given x,y,z∈R+ ,and 3x=4y=6z .Then write 3x, 4y, and 6z in order from least to greatest as ___.