(x+y)/2+(x-y)/3=-5 (x+y)/2-(x-y)/3=-1设a=(x+y)/2, b=(x-y)/3a+b=-5a-b=-1解得：a=-3；b=-2(x+y)/2=-3, x+y=-6(x-y)/2=-1, x-y=-2解得：x=-4y=-2
