$ D = 100^2 + 103^2 + 105^2 + 94^2 - (101^2 + 98^2 + 96^2 + 107^2) \\ = 100^2 + 103^2 + 105^2 + 94^2 - 101^2 - 98^2 - 96^2 - 107^2 \\ = 100^2 - 98^2 + 103^2 - 101^2 + 105^2 - 107^2 + 94^2 - 96^2 \\ = (100 + 98)(100 - 98) + (103 + 101)(103 - 101) + (105 + 107)(105 - 107) + (94 + 96)(94 - 96) \\ =...