1.(1/69+2/71)乘23+25除以71 =1/69*23+2/71*23+25/71 =1/3+(46/71+25/71) =1/3+1 =4/3 2.(1+1/2)乘(1-1/2)乘(1+1/3)乘(1-1/3)乘.乘(1+1/9)乘(1-1/9) =3/2*1/2*4/3*2/3...*10/9*8/9 =1/2*10/9(中间的都约去了） =5/9 ...