계산: 11 × 2 + 12 × 3 + 13 × 4 + 14 × 5 +...+ 12005 × 2006 =

계산: 11 × 2 + 12 × 3 + 13 × 4 + 14 × 5 +...+ 12005 × 2006 =

11 × 2 + 12 × 3 + 13 × 4 + 14 × 5 +...+ 12005 × 2006 = 1 - 12 + 12 - 13 + 14 + 15 +...+ 12005 - 2006 = 1 - 12006 = 20052006