Bài 1:Tính nhanh. a)15/13-(4/9+2/13) b)7 4/9-4 7/11)-(3 4/9-2 7/11) c) -7/9.4/11+-7/9.7/11+5 7/9 d)18/23+5/23.1 2/29-5/23.2/29

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1. `15/13-(4/9+2/13)`

   `= 15/13-4/9-2/13`

   `= (15/13-2/13)-4/9`

   `= 1 – 4/9`

   `= 5/9`

   (`7 “4/9-4` `7/11)-(3` `4/9-2` `7/11`)

   `= 7 “4/9-4` `7/11-3` `4/9+2` `7/11`

   `= (7 “4/9 -3` `4/9) + (2` `7/11 -4` `7/11`)

   `= 4+ (-2)`

   `= 2`

   `(-7/9) . 4/11+ (-7/9) . 7/11+5` `7/9`

   `= (-7/9) . (4/11+ 7/11) +5` `7/9`

   `=  (-7/9) . 1 +5` `7/9`

   `= (-7/9) + 5 + 7/9`

   `= 5`

   `18/23 + 5/23 . 1` `2/29 – 5/23 . 2/29`

   `18/23 + 5/23 . (1` `2/29 –  2/29)`

   `= 18/23 + 5/23 . 1`

   `= 18/23 + 5/23 `

   `= 1`

   (Chúc bạn học tốt)

    

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2. Đáp án:

    `a)` `5/9`

   `b)` `2`

   `c)` `5`

   `d)` `1`

   Giải thích các bước giải:

   `a)` `15/13-(4/9+2/13) `

   `=15/13-4/9-2/13`

   `=(15/13-2/13)-4/9`

   `=1-4/9`

   `=5/9`

    `b)` `(7(4)/9-4(7)/11)-(3(4)/9-2(7)/11)`

   `=7(4)/9-4(7)/11-3(4)/9+2(7)/11`

   `=(7(4)/9-3(4)/9)-(4/(7)/11-2(7)/11`

   `=4-2`

   `=2`

   `c)` `(-7)/9×4/11+(-7)/9×7/11+5(7)/9`

   `=(-7)/9×(4/11+7/11)+5(7)/9`

   `=(-7)/9+5(7)/9`

   `=5`

   `d)` `18/23+5/23×1(2)/29-5/23×2/29`

   `=18/23+5/23×(1(2)/29-2/29)`

   `=18/23+5/23`

   `=1`

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