{[(−1234) + (−4230)] − 75} + 4230 2. − 1 3 3 − 3. 1 3 2 + 4. − 1 3 + 1 1 999 + 13 888 − 5 777 . 1 − 3 4 − 1 12 − 1 6 A = 1 + 2 + + 1000 B = 1 + 3 + 5 + + 2009 C = 2 + 4 + 6 + + 2008 D = 100 + 102 + 104 + 2080 2 500 3 300 27 5 4.9 7 2012 50 + 2012 49 2013 50 xOx xx Oy Oz xOz = 45 0 x Oy = 90 0 Ox, Oy, Oz Oz xOy Oz x Oy zOz =?