If the tolerance of arithmetic sequence an is - 1 and a1 + A2 + a3 +... + A2008 = 5022, then A2 + A4 + A6 +... + A2008 =?

If the tolerance of arithmetic sequence an is - 1 and a1 + A2 + a3 +... + A2008 = 5022, then A2 + A4 + A6 +... + A2008 =?

Because A1 = A2 + 1, A3 = A4 + 1 A2007 = A2008 + 1, so a1 + A2 + a3 +... + A2008 = A2 + A4 + A6 +... + A2008 + A2 + A4 + A6 +... + A2008 + 2008 / 2 = 2 (A2 + A4 + A6 +... + A2008) + 2008 / 2 = 5022a2 + A4 + A6 +... + A2008 = (5022-2008 / 2) / 2 = 2009

If for any non-zero rational numbers a and B, the definition of operation a △ B is as follows: a △ B = (a-b) / ab. try to find the value of 3 △ 4 △ 5

Oh, flying geese,
4△5＝（4－5）/（4×5）＝－0.05
3△（4△5）＝3△（－0.05）＝（3＋0.05）/3×（－0.05）＝－3.05/0.15＝－61/3

For integers a, B, C, D, the symbol ∣ ad - BC ∣ denotes the operation AC – BD. given that 1 ∣ 1D - BC ∣ 3, what is the value of B + D?

1