Old people should to politely.
A:speak
B:be spoken
C:to speak
设函数f(x)=xm+ax的导数f′(x)=2x+1,则数列1f(n) n∈(N*)的前n项和( )
口 ____ ____ 氵 ____ ____ 亻 ____ ____
木 ____ ____ 心 ____ ____ 广 ____ ____