2x+y=m- 1,(2)
(1)-(2): x+y=2, substitute (2): x+2=m- 1, x=m-3,
Then y = 2-x = 2-(m-3) = 5-m.
x-y=m-3-(5-m)=2m-8=2(m-4)
When m> is at four o'clock, M-4 > 0,x-y & gt; 0,x & gty
A: m> IV