( 1) a? =-a
Then a=0 or a=- 1.
If a = 0 and m = {0 0,0}, it contradicts the anisotropy of the set.
If a=- 1, M = {1,-1}, N = {1, -3}, MUN={ 1,-1, 3}
At this time, M∩N ={ 1}
(2) a? =2a- 1
At this time a= 1.
M={ 1, 1}, which contradicts the set.
(3)a=-a
At this time, a=0, m = {0,0}, which contradicts the anisotropy of the set.
(4)a=2a- 1
At this time, a= 1 M={ 1, 1}, which contradicts the anisotropy of the set.
To sum up, a=- 1, M∩N ={ 1}