1-1/6+1/42+1/56+1/72+1/90=24/30+(1/30+1/42+1/56+1/72+1/90)=4/5+1/(5x6)+1/(6x7)+1/(7x8)+1/(8x9)+1/(9x10)=4/5+(1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)=4/5+1/5-1/10=0.9 朋友,我都还没发上来,你怎么就给我采纳了呢?
5/6+1/42+1/56+1/72+1/90=36/42+1/56+1/72+1/90=49/56+1/72+1/90=63/72+1/90=81/90=0.9
我来帮你朋友,但先问一下是1减(分之1加42分之1加56分之1加72分之1加90分之1)的和还是就1减6分之1加42分之1加56分之1加72分之1加90分之1呢?
0.9