—Mr. Smith, would you please speak a little more ________?—Sorry! I thought you could follow me.
A:quietly
B: slowly
C:quickly
D:politely
观察下列在中国出土的唐代文物——货币,这些出土文物说明了( )
A=x|x=2k,k∈Z,B=x|x=2k+1,k∈Z,C=x|x=4k+1,k∈Z,又a∈A,b∈B则( )
如图,PA、PB切⊙O于A、B两点,CD切⊙O于点E,分别交PA、PB于点C、D.若PA、PB的长是关于x的一元二次方程x2﹣mx+m﹣1=0的两个根,求△PCD的周长.