tinh nhanh 4/45+-1/15+7/45+4/15+-2/45+-1/5 1/2+-1/3+1/4+-1/5+1/6+-1/6+1/5+-1/4+1/3+-1/2

Đáp án + Giải thích các bước giải:

`1/2` + (-`1/3`) + `1/4` + (-`1/5`) + `1/6` + (-`1/7`) + `1/8` + `1/7` + (-`1/6`) + `1/5` + (-`1/4`) +`1/3` + (-`1/2`)

= `1/2` - `1/2` -`1/3` + `1/3` +`1/4` - `1/4` -`1/5` + `1/5 `+`1/6` - `1/6` - `1/7` + `1/7` + `1/8`

= `1/8`

Đáp án + Giải thích các bước giải:

`4/45 + (-1)/15 + 7/45 + 4/15 + (-2)/45 + (-1)/5` $\\$ `= (4/45 + 7/45 - 2/45) - 1/5 + ((-1)/15 + 4/15)` $\\$ `= 9/45 - 1/5 + 3/15` $\\$ `= 1/5 - 1/5 + 1/5` $\\$ `= 0 + 1/5` $\\$ `= 1/5`

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`1/2 + (-1)/3 + 1/4 + (-1)/5 + 1/6 + (-1)/6 + 1/5 + (-1)/4 + 1/3 + (-1)/2` $\\$ `= 1/2 - 1/3 + 1/4 - 1/5 + 1/6 - 1/6 + 1/5 - 1/4 + 1/3 - 1/2` $\\$ `= (1/2 - 1/2) + (1/3 + 1/3) + (1/4 - 1/4) + (1/5 - 1/5) + (1/6 - 1/6)` $\\$ `= 0 + 0 + 0 + 0 + 0` $\\$ `= 0`