此题主要运用:括号前面是减号时,添加括号或者去掉括号,括号里面的符号都变号。3/5-1/4+2/5-3/4=(3/5+2/5)-(1/4+3/4)=1-1=0
=(3/5+2/5)-(1/4+3/4)=1-1=0
(3/5+2/5)-(1/4+3/4)=1-1=0
3/5-1/4+2/5-3/4=(3/5+2/5)-(1/4+3/4)=1-1=0