世界上最湿润的大洲是( )
已知函数f(x)=x2+5x+4,x≤02x-2,x>0,若函数y=f(x)﹣a|x|恰有4个零点,则实数a的取值范围为____
下面句中只有一处错误,请找出并改正。
Everyone on the farm are singing and dancing together.
____
已知数列{an}的前n项和为Sn,且满足an=2Sn+1(n∈N*).
(Ⅰ)求数列{an}的通项公式;
(Ⅱ)若bn=(2n﹣1)•an,求数列{bn}的前n项和Tn.