2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 2+4-6+8-10+12-14+16-18+20-22+24-26+28=? （口算）4+6+8+10+12+14+16+18+20+22+24+26+28+30+32+34+36． 1行 2 4 6 8 2 行 16 14 12 10 3行 18 20 22 24 4行 32 30 28 26 问：第 若干个偶数按每行8个数排成一行:2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32, 2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,数字6个1组.点组 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40圈的是6, 2 4 6 8 16 14 12 10 18 20 22 24 32 30 28 26 34 36 38 40 48 4 2+4+6+8+10+12+14+16+18+20+22+24+26+28+30+32+34+36+38+40+42+4 数列 把正偶数按下面数阵排列 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 . 则第 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 求一数列的通项公式1,2,3,4,5,6,7,8,9,10,12,14,16,18,20,22,24,26,28,30,