4. a) A = { -3 ; 3 }
d) D = { -17 ; 17 }
5. a) |-2| + |27| = 2 + 27 = 29
f) |-29| - |43| = 29 + 43 = 72
6. a) = 2 - 55 + 12 = -53 +12 = -41
f) = 5 - 79 + 27 = -72 + 27 = -45