1/30+1/42+1/56+1/72=

来源：学生作业帮助网编辑：作业帮时间：2024/04/29 01:31:33

1/30+1/42+1/56+1/72=
1/30+1/42+1/56+1/72=

1/30+1/42+1/56+1/72=
原式=1/(5×6)+1/(6×7)+1/(7×8)+1/(8×9)
=(6-5)/(5×6)+(7-6)/(6×7)+(8-7)/(7×8)+(9-8)/(8×9)
=6/(5×6)-5/(5×6)+7/(6×7)-6/(6×7)+8/(7×8)-7/(7×8)+9/(8×9)-8/(8×9)
=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/5-1/9
=9/45-5/45
=4/45

原式=1/(5x6)+1/(6x7)+1/(7x8)+1/(8x9)=1/5-1/9=4/45

1/30+1/42+1/56+1/72
=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/5-1/9
=4/45

1/30+1/42+1/56+1/72
=1/5*6+1/6*7+1/7*8+1/8*9
=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/5-1/9
=4/45

1/30+1/42+1/56+1/72= 1/30+1/42+1/56+1/72+1/90 1/30+1/42+1/56+1/72+1/90 1/12+1/20+1/30+1/42+1/56+1/72+1/90=? 1/6+1/12+1/20+1/30+1/42+1/56+1/72=? 1/30+1/42+1/56+1/72 简算 1/30+1/42+1/56+1/72简便算法 1/30+1/42+1/56+1/72＝简算1/30+1/42+1/56+1/72＝? 1/30+1/42+1/56+1/72+1/90+1/110=? 1/30+1/42+1/56+1/72+1/90=简便计算 20分之1+30分之1+42分之1+56分之1+72分之1=? 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90== 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90= 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+190+1/110=? 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=多少 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+.1/9900=? 简便计算：1/30+1/42+1/56+1/72=急