A) (5/4x-1/3):1/3=1.4 B) 2/7:(0.25x-4/5)=5/21 C) |x-2/3|=1

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1. Đáp án:

   a)(5/4x-1/3):1/3=1.4

   <=>5/4x+1/3 = 1.4 x 1/3

   <=>5/4x = 1/12 – 1/3

   <=>x = -1/4 : 5/4 = -1/5

   b) 2/7:(0.25x-4/5)=5/21

   <=> 0,25x – 4/5 = 2/7 : 5/21

   <=> 0,25x = 6/5 + 4/5

   <=> x = 2 : 0,25 = 8

   c)|x-2/3|=1 

   +)x- 2/3 = 1                            +) x – 2/3 = -1

   <=>    x = 5/3                            <=>   x = -1/3

   Vậy x      = 5/3                hoặc               x = -1/3 

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2. a) `(5/4 x – 1/3) : 1/3 = 1.4`

   `(5/4 x – 1/3) = 4 .1/3`

   `5/4 x – 1/3 = 4/3`

   `5/4 x = 4/3 + 1/3`

   `5/4 x = 5/3`

   `x= 5/3 : 5/4`

   `x= 5/3 . 4/5`

   `x= 4/3`

   Vậy `x= 4/3`

   b) `2/7 : (0,25 x – 4/5) = 5/21`

   `0,25 x – 4/5 = 2/7 : 5/21`

   `0,25 x – 4/5 = 2/7 . 21/5`

   `1/4 x – 4/5= 6/5`

   `1/4x = 6/5 + 4/5`

   `1/4 x= 2`

   `x= 2:1/4`

   `x= 2.4`

   `x= 8`

   Vậy `x =8`

   c) `|x -2/3 | =1`

   +) `x – 2/3 =1`

   `=> x = 1 + 2/3`

   `=> x= 5/3`

   +) `x -2/3 = -1`

   `=> x= -1 + 2/3`

   `=> x= -1/3`

   Vậy `x= -1/3` hoặc `x= 5/3`

    

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