Tìm x, biết: a)2/3.x-1/2=1/10 b)-2/3.x+1/5=3/10 c)(4/5.x-5):2/3=-5

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1. `a )“2/3.x-1/2=1/10`

   `2/3.x    = 1/10 + 1/2`

   `2/3.x    = 1/10 + 5/10`

   `2/3.x    = 6/10 = 3/5`

   `2/3.x    = 3/5`

   `    x    = 3/5 : 2/3`

   `    x    = 3/5 . 3/2`

   `    x    = 9/10`

   `b )“(-2)/3.x+1/5=3/10`

   `(-2)/3.x    = 3/10 – 1/5`

   `(-2)/3.x    = 3/10 – 2/10`

   `(-2)/3.x    = 1/10`

   `       x    = 1/10 : ( -2 )/3`

   `       x    = 1/10 . 3/( -2 )`

   `       x    = 3/-20` 

   `c )“(4/5.x-5):2/3=-5`

   `(4/5.x-5)    = -5 . 2/3`

   ` 4/5.x-5     =  (-10 )/3`

   ` 4/5.x       =  (-10 )/3 + 5`

   ` 4/5.x       =  (-10 )/3 + 5/1`

   ` 4/5.x       =  ( -10 )/3 + 15/3`

   ` 4/5.x       =  5/3`

   `     x       =  5/3 : 4/5`

   `     x       =  5/3 . 5/4`

   `     x       =  25/12`

    

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2. Đáp án:

   `2/3x – 1/2 = 1/10`

   `-> 2/3x = 3/5`

   `-> x = 9/10`

   `-2/3x + 1/5 = 3/10`

   `-> -2/3x = 1/10`

   `-> x = (-3)/20`

   `(4/5x – 5) : 2/3 = -5`

   `-> 4/5x – 5 = (-10)/3`

   `-> 4/5x = 5/3`

   `-> x = 25/12`

    

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