液压马达的机械效率为()与()之比。
参考答案:实际转矩;理论转矩
Mr. Bean’s movies are always very_________ and many people are made to laugh.
A.boring
B.sad
C.funny
D.successful
设函数f(x)在R上的导函数为f′(x),且2f(x)+xf′(x)>x2,下面的不等式在R内恒成立的是( )
A.f(x)>0
B.f(x)<0
C.f(x)>x
D.f(x)<x