5＞2(1-x1),1-x1＜2.5,x1＞-1.5,x1=-1,0
11-x2＞1-3x2,2x2＞-10,x2＞-5,x2=-4,-3,-2,-1,0
x1+x2=-1+0-4-3-2-1+0=-11