简算：1.（19/20)+(29/30)+(41/42)+(55/56)解,得：==(1-1/20)+(1-1/30)+(1-1/42)+(1-1/56)==4-1/20-1/30-1/42-1/56==4-（1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8）==4(1/4-1/8)==4*(1/8)==1/2