可以啊-2/3和+2/3可以抵消,剩下的就是4/5+1/5=1
根据加法结合率,可以把原式看成: (4/5+1/5)-(2/3-2/3) =1+0 =1
用加法交换率和结合律4/5+1/5-(2/3-2/3)=1-0=1
(4/5+1/5)-(2/3-2/3) =1+0 =1
4/5-2/3+1/5+2/3 =4/5+1/5+2/3-2/3=4/5+1/5=1