Cho mình xin lời giải đáp án đúng nhất nha mình sẽ votes cho 5 **

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Đáp án+Giải thích các bước giải:

Câu 17. `A=1/(1xx2)+1/(2xx3)+1/(3xx4)+...+1/(99xx100)`

`A=1-1/2+1/2-1/3+1/3-1/4+...+1/99-1/100`

`A=1-1/100=99/100`

Câu 18. `B=1/(1xx3)+1/(3xx5)+1/(5xx7)+...+1/(99xx101)`

`2B=2/(1xx3)+2/(3xx5)+2/(5xx7)+...+2/(99xx101)`

`2B=1-1/3+1/3-1/5+1/5-1/7+...+1/99-1/101`

`2B=1-1/101=100/101`

`B=100/101:2`

`B=50/101`

Câu 19. `C=1/(2xx4)+1/(4xx6)+1/(6xx8)+...+1/(98xx100)`

`2C=2/(2xx4)+2/(4xx6)+2/(6xx8)+...+2/(98xx100)`

`2C=1/2-1/4+1/4-1/6+1/6-1/8+...+1/98-1/100`

`2C=1/2-1/100=49/100`

`C=49/100:2`

`C=49/200`

Câu 20. `D=1+1/3+1/6+1/10+...+1/630`

`D=1+2/6+2/12+2/20+...+2/1260`

`D=1+(2/6+2/12+2/20+...+2/1260)`

`D=1+(2/(2xx3)+2/(3xx4)+2/(4xx5)+...+2/(35xx36))`

`D=1+2(1/(2xx3)+1/(3xx4)+1/(4xx5)+...+1/(35xx36))`

`D=1+2(1/2-1/3+1/3-1/4+1/4-1/5+...+1/35-1/36)`

`D=1+2(1/2-1/36)`

`D=1+2 . 17/36`

`D=1+17/18`

`D=35/18`

Câu 21. `E=1/2+1/4+1/8+1/16+1/32+...+1/512+1/1024`

`2E=1+1/2+1/4+1/8+1/16+...+1/256+1/512`

`2E-E=1+1/2+1/4+1/8+1/16+...+1/256+1/512-1/2-1/4-1/8-1/16-...-1/256-1/512`

`E=1-1/512`

`E=511/512`

Câu 22. `G=1/3+1/9+1/27+1/81+1/243+1/729+1/2187`

`G=1/3+1/9+...+1/2187`

`3G=1+1/3+...+1/729`

`3G-G=1+1/3+...+1/729-1/3-1/9-...-1/2187`

`2G=1-1/2187`

`2G=2186/2187`

`G=2186/2187:2`

`G=1093/2187`

Câu 23. `H=1/(1xx2xx3)+1/(2xx3xx4)+1/(3xx4xx5)+...+1/(98xx99xx100)`

`2H=2/(1xx2xx3)+2/(2xx3xx4)+2/(3xx4xx5)+...+2/(98xx99xx100)`

`2H=1/(1xx2)-1/(2xx3)+1/(2xx3)-1/(3xx4)+1/(3xx4)-1/(4xx5)+...+1/(98xx99)-1/(99xx100)`

`2H=1/(1xx2)-1/(99xx100)`

`2H=1/2-1/9900`

`2H=4949/9900`

`H=4949/9900:2`

`H=4949/19800`