Question

已知方程组x+y=-7-m①,x-y=1+3m②

Answer 1

x-y=1+3m....（1）
x+y=－7-m...(2)
(1)+(2)x=m-3
(2)-(1)y=-2m-4

1.x为非正数x≤0，y为负数,y<0,即-2<m<=3

2.由（1）
│m-3│-│m+2│=3-m-(m+2)=-2m+1

3.2mx+x<2m+1
2m(x-1)<1-x
由x>1得 m<- 1/2
由1知 -2<m<=3
故m=-1
请采纳。

Answer 2

x-y=1+3m①
x+y=－7-m②
①+②得 2x=2m-6 x=m-3
②-①得 2y=-8-4m y=-4-2m

1.x为非正数x≤0，y为负数,y<0,即-2<m<=3

2.由①
│m-3│-│m+2│=3-m-(m+2)=-2m+1

3.2mx+x<2m+1
2m(x-1)<1-x
由x>1得 m<- 1/2
由①知 -2<m<=3
故m=-1