题目

(-二分之一)+(+三分之一)+(-四分之一)+(+九分之一)+(+八分之一)+(-九分之四)=

提问时间：2020-07-18

答案

原式=(-1/2)+(+1/3)+(-1/4)+(+1/9)+(+1/8)+(-4/9)
=[(+1/9)+(-4/9)]+(+1/3)+[(-1/2)+(-1/4)]+(+1/8)
=[-(4/9-1/9)]+(+1/3)+[-(1/2+1/4)]+(+1/8)
=[(-1/3)+(+1/3)]+[(-3/4)+(+1/8)]
=0+[-(3/4-1/8)]
=-(6/8-1/8)
=-5/8