代数式3a+4b可以表示不同的实际意义,试举实例说明:____
在测额定电压为2.2V小灯泡的额定功率实验中,电源电压为4.5V.如图所示:
—Could you please tell me ____________?
—Because it's very helpful.
已知函数fx{0x>oπx=0π2+1x<0,则fff-1的值等于( )