Toán 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90 = 08/09/2021 By Kinsley 1/2 + 5/6 + 11/12 + 19/20 + 29/30 + 41/42 + 55/56 + 71/72 + 89/90 =
`1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90` `=1-1/2+1-1/6+1-1/12+1-1/20+1-1/30+1-1/42+1-1/56+1-1/72+1-1/90` `=(1+1+…+1)-(1/2+1/6+1/12+…+1/90)` `=9-(1/1.2+1/2.3+1/3.4+…+1/9.10)` `=9-(1-1/2+1/2-1/3+1/3-1/4+…+1/9-1/10)` `=9-(1-1/10)` `=9-1+1/10` `=`$8\frac{1}{10}$ P/s: Dấu . là dấu nhân nhó ‘-‘ Trả lời
1+1=2
`1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90`
`=1-1/2+1-1/6+1-1/12+1-1/20+1-1/30+1-1/42+1-1/56+1-1/72+1-1/90`
`=(1+1+…+1)-(1/2+1/6+1/12+…+1/90)`
`=9-(1/1.2+1/2.3+1/3.4+…+1/9.10)`
`=9-(1-1/2+1/2-1/3+1/3-1/4+…+1/9-1/10)`
`=9-(1-1/10)`
`=9-1+1/10`
`=`$8\frac{1}{10}$
P/s: Dấu . là dấu nhân nhó ‘-‘