2x-y=2m-1 .(1)
-x+3y=m.(2)
(1)+(2)*2得
5y=4m-1
y=(4m-1)/5
代入(2)得
2x-(4m-1)/5=2m-1
10x-4m+1=10m-5
10x=14m-4
x=(7m-2)/5
x+2y
=(15m-4)/5≤0
15m-4≤0
15m≤4
m≤4/15