(1)
A={x| 0≤x-m≤3 },B={x| x
m≥0 and 3+m ≤ 3
m≥0 and m ≤0
=> m=0 #
(2)
A∪B=B => A is subset of B
3+m< 0 or m>3
m< -3 or m > 3 #