bài 5: rút gọn biểu thức sau :( tính nhanh nếu có thể) 1) -5/7.2/11+-5/7.9/11+1 và 5/7 2). 6/7+5/8:5–3/16.(-2)^2 3). 2/3+1/3.( -4/9+5/6) :7/12 Mik

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1. `1) ( – 5 )/7 . 2/11 + ( – 5 )/7 . 9/11 + 1 5/7`

   `= ( – 5 )/7 . ( 2/11 + 9/11 ) + 12/7`

   `= ( – 5 )/7 . 1 + 12/7`

   `= ( – 5 )/7 + 12/7`

   `= 1`

   `2) 6/7 + 5/8 : 5 – 3/16 . ( – 2 )^2`

   `= 6/7 + 5/8 . 1/5 – 3/16 . 4`

   `= 6/7 + 1/8 – 3/4`

   `= 48/56 + 7/56 – 42/56`

   `= 55/56 – 42/56`

   `= 13/56`

   `3) 2/3 + 1/3 . ( ( – 4 )/9 + 5/6 ) : 7/12`

   `= 2/3 + 1/3 . ( ( – 16 )/36 + 30/36 ) : 7/12`

   `= 2/3 + 1/3 . 7/18 : 7/12`

   `= 2/3 + 1/3 . 7/18 . 12/7`

   `= 2/3 + 1/3 . 2/3`

   `= 2/3 + 2/6`

   `= 4/6 + 2/6`

   `= 1`

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2. Đáp án:

   `1,`

   `(-5)/7 × 2/11 + (-5)/7 × 9/11 + 1 5/7`

   `= (-5)/7 × (2/11 + 9/11) + 12/7`

   `= (-5)/7 × 1 + 12/7`

   `= (-5)/7 + 12/7`

   `= 1`

   `2,`

   `6/7 + 5/8 ÷ 5 – 3/16 × (-2)^2`

   `= 6/7 + 1/8 – 3/16 × 4`

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

   `= 6/7 + (1/8 – 3/4)`

   `=6/7 + (-5/8)`

   `= 13/56`

   `3,`

   `2/3 + 1/3 × (-4/9 + 5/6) ÷ 7/12`

   `= 2/3 + 1/3 × 7/18 × 12/7`

   `= 2/3 + 1/3 × 2/3`

   `= 2/3 + 2/9`

   `= 8/9`

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