下列四个函数中，当x增大时，y值减小的函数是（） A．y=3x B．y=2x+

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问题选择题

下列四个函数中，当x增大时，y值减小的函数是（　　）

A．y=3x

B．y=2x+1

C．y=2x-1

D．y=-x+1

答案

因为满足x增大时，y值减小的函数，必须k＜0．

故选D．

选择题

It was not ________ the many blows he received ________ the lack of fighting spirit________ led to his losing the game.

A．so; for; which

B．so much; as; that

C．like; for; that

D．as; as; which

单项选择题

已知正弦交流电的电压V=310sint，频率f=50HZ，则在t=0.1秒时电压的瞬时值为（）伏。

A.220

B.310

C.110

D.0