Đáp án+Giải thích các bước giải:
`2.4`
`A=1/3-3/4-(-3/5)+1/(72)-2/9-1/(36)+1/(15)`
`A=1/3-3/4+3/5+1/(72)-2/9-1/(36)+1/(15)`
`A=(1/3+3/5+1/(15))+[(-3/4)-2/9-1/(36)]+1/(72)`
`A=(5/(15)+9/(15)+1/(15))+[(-27/36)-8/(36)-1/(36)]+1/(72)`
`A=15/15+(-36/36)+1/(72)`
`A=1+(-1)+1/(72)`
`A=0+1/(72)`
`A=1/(72)`
Vậy `A=1/(72)`
`2.5`
`B=1/5-3/7+5/9-2/(11)+7/(13)-9/(16)-7/(13)+2/(11)-5/9+3/7-1/5`
`B=(1/5-1/5)+[(-3/7)+3/7]+(5/9-5/9)+[(-2/(11))+2/(11)]+(7/(13)-7/(13))-9/(16)`
`B=0+0+0+0+0-9/(16)`
`B=-9/(16)`
Vậy `B=-9/(16)`
`2.6`
`C=1/(100)-1/(100.99)-1/(99.98)-1/(98.97)-...-1/(3.2)-1/(2.1)`
`C=1/(100)-(1/(100.99)+1/(99.98)+1/(98.97)+...+1/(3.2)+1/(2.1))`
`C=1/(100)-(1/(1.2)+1/(2.3)+...1/(97.98)+1/(98.99)+1/(99.100))`
`C=1/(100)-(1-1/2+1/2-1/3+...+1/9-1/(98)+1/(98)-1/(99)+1/(99)-1/(100))`
`C=1/(100)-(1-1/(100))`
`C=1/(100)-1+1/(100)`
`C=2/(100)-1`
`C=1/(50)-1`
`C=1/(50)-50/50`
`C=-49/50`
Vậy `C=-49/50`
