a)-5/7×1/3+2/3×-5/7+5/7×11/19–8/19×5/7 b)11/169+-2/3+-18/31–15/169–18/31

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1. Đáp án + Giải thích các bước giải:

    `a)` `(-5)/7. 1/3+2/3.(-5)/7+5/7. 11/19-  (-8)/19. 5/7`

   `= (-5)/7.(1/3+2/3)+5/7.(11/19+8/19)`

   `= (-5)/7 .1 + 5/7 .1`

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

   `= 0`

   `b)` `11/169 + (-2)/3+(-18)/31- (-15)/169- (-18)/31`

   `= (11/169+15/169)+((-18)/31+18/31)+ (-2)/3`

   `= 26/169+0+(-2)/3`

   `= 2/13+(-2)/3`

   `= 6/39+ (-26)/39`

   `= (-20)/39`

    

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2. a)(-5/7)×1/3+2/3×(-5/7)+5/7×11/19-(-8/19)×5/7

   = -5/17 × ( 1/3 +2/3 ) + 5/7 × (11/19-(-8/19))

   = -5/17 × 1 + 5/7 × 1

   = -5/7 + 5/7

   = 0

   b, 11/169+(-2/3)+(-18/31)-(-15/169)-(-18/31)

   = 11/169 – 2/3- 18/31 + 15/169 +18/31

   = (11/169 + 15/169 ) – 2/3 – ( 18/31 – 18/31)

   = 26/169 – 2/3 -0

   = 2/13 – 2/3 – 0

   = -20/39 – 0

   = -20/39

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