当x≤-2时,x+2≤0,x-1＜0
原式=-(x+2)+(x-1)
=-x-2+x-1
=-3
当-2＜x＜1时,x+2＞0;x-1＜0
原式=x+2+x-1
=2x+1
当x≥1时,x+2＞0,x-1≥0
原式=x+2-(x-1)
=x+2-x+1
=3