当 x < -2 时,y= -(x+2)-(x-1)-(x-5) = -3x+4 > 6+4=10 ;
当 -2 ≤ x < 1 时,y = (x+2)-(x-1)-(x-5) = -x+8 > -1+8=7 ;
当 1 ≤ x < 5 时,y = (x+2)+(x-1)-(x-5) = x+6 ≥ 1+6=7 ;
当 x ≥ 5 时,y = (x+2)+(x-1)+(x-5)=3x-4≥15-4=11 ,
综上,当 x = 1 时,y 最小值为 7 .
当 x < -2 时,y= -(x+2)-(x-1)-(x-5) = -3x+4 > 6+4=10 ;
当 -2 ≤ x < 1 时,y = (x+2)-(x-1)-(x-5) = -x+8 > -1+8=7 ;
当 1 ≤ x < 5 时,y = (x+2)+(x-1)-(x-5) = x+6 ≥ 1+6=7 ;
当 x ≥ 5 时,y = (x+2)+(x-1)+(x-5)=3x-4≥15-4=11 ,
综上,当 x = 1 时,y 最小值为 7 .