(-2/7+1/6-3/谨歼漏14+2/3)/(-1/42) =(2/7-1/6+3/14-2/3)/(1/42) =42*(2/7-1/6+3/14-2/改世3)=42*2/祥烂7-42*1/6+42*3/14-42*2/3=12-7+9-28=-14
=-42(-2/7+1/6-3/14+2/3)=-(-12+7-9+28)=-14
