1) if AB∨y axis, the abscissas of a and b are equal, but the ordinate is different, so a- 1=-3, B+ 1≦-2.

So a=-2, b≦-3.

2) If the abscissa of A and B are not equal and the ordinate is equal on the AB∑X axis, then A- 1≦-3, b+ 1=-2.

So a≦-2, b=-3.

3)a- 1= 3，b+ 1= 2

So a=4 or -2, and b = 1 or -3.

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