说出下面各数列的首项、末项、项数。如果是等差数列,并找出公差。
(1)3,9,15,21,27,33,39,45,51
(2)1,2,3,4,5,...,25,26,27
(3)93,90,87,84,81,78,75,72,69,66
(4)4,5,9,14,23,37,60,97