Question

已知|x+3y+6|与|2x-y+5|互为相反数,求x+y-xy的值

Answer 1

|x+3y+6|与|2x-y+5|互为相反数,所以各自为0

x+3y=-6

2x-y=-5

解得y=-1,x=-3

x+y-xy=-3-1-3*1=-7