(x+6)/(4-x)<=1(x+6)/(4-x)-1<=0(x+6-4+x)/(4-x)<=0(2x+2)/(4-x)<=0(x+1)/(4-x)<=0-(x+1)/(x-4)<=0(x+1)/(x-4)>=0相当于(x+1)(x-4)>=0x<=-1或x>4
(x+6)/(4-x)≤1x+6≦4-xx+x≤4-62x≤-2x≤-1
