A=｛(x,y)丨x^2+mx-y+2=0}
= { (x,y) | y=x^2+mx+2}
B=｛（x,y)丨x-y+1=0 且0≤x≤2｝
= ｛（x,y)丨y=x+1且0≤x≤2｝
A∩B≠空集, then
x^2+mx+2 = x+1
x^2+(m-1)x+1=0
for real roots
△≥0
(m-1)^2 - 4 ≥0
m^2 -2m -3 ≥0
(m-3)(m+1)≥0
-1≤m≤3