Given that the elements (x, y) in the set a correspond to the elements (x + y, X-Y) in the set B under the mapping f, then the elements (4, - 2) in the set B correspond to the elements (x + y, X-Y) in the set a__________ x+y=4, x-y=-2 x=1,y=3. (1,3) Why not the other way around? x+y=-2, x-y=4?

Given that the elements (x, y) in the set a correspond to the elements (x + y, X-Y) in the set B under the mapping f, then the elements (4, - 2) in the set B correspond to the elements (x + y, X-Y) in the set a__________ x+y=4, x-y=-2 x=1,y=3. (1,3) Why not the other way around? x+y=-2, x-y=4?

According to the definition of set element (a, b), the position of each number in the element is determined, and the position cannot be reversed. In the question (4, - 2), 4 corresponds to the position of X + y, and - 2 corresponds to the position of X-Y. therefore, it cannot be reversed