【简答题】若3x等于5y,则x:y=______.
【单选题】在比例控制系统,若比例度远小于临界比例度δk,则过渡过程属于( )
【简答题】先化简,再求值: (1)若x=﹣1,y=0.5,则(x﹣5y)(﹣x﹣5y)﹣(﹣x+5y) 2 =( ); (2)若x=2,y=﹣3,则 =( )。
【简答题】数据帧是由终端系统发出的,它们的源和目的地址在经过交换机时是 。
【单选题】When the "invisible hand" guides economic activity, prices of products reflect
A.
only the values that society places on those products.
B.
only the costs to society of producing those products.
C.
both the values that society places on those products and the costs to society of producing those products.
D.
none of the above; when the "invisible hand" guides economic activity, prices of products are set by the government in a manner that is thought to be "fair."
【单选题】在比例控制系统,若比例度远小于临界比例度δk,则过渡过程属于( )
【单选题】宽带(宽频)探头,不包括下列含义
B.
接收所有频率,即2~12MHz回声,包括近远程
C.
接收所有频率限于中近程,远程只能接收较低频率
E.
近程取高频,中程取中频,远程按低频,即动态接收