Bài 2B : Tìm số nguyên x a) 21+(2x-14)=23 b) 1-(12+3x)=7 c) -(2x+2)+25=-19 d) 26-(26-x)=0

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1. Bài 2B:

   a) `21+(2x-14)=23`

   `2x-14=23-21`

   `2x-14=2`

   `2x=14+2`

   `2x=16`

   `x=16: 2`

   `x=8`.

   Vậy `x=8`.

   b) `1-(12+3x)=7`

   `12+3x=1-7`

   `12+3x=-6`

   `3x=-6-12`

   `3x=-18`

   `x=-18: 3`

   `x=-6`.

   Vậy `x=-6`.

   c) `-(2x+2)+25=-19`

   `-(2x+2)=-19-25`

   `-(2x+2)=-44`

   `=> 2x+2=44`

   `=> 2x=44-2`

   `=> 2x=42`

   `=> x=42: 2`

   `=> x=21`.

   Vậy `x=21`.

   d) `26-(26-x)=0`

   `26-26+x=0`

   `0+x=0`

   `x=0`.

   Vậy `x=0`.

    

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2. `21+(2x-14)=23`

   ` 2x – 14 = 23 – 21`

   `2x – 14 = 2`

   `2x = 2 + 14`

   `2x = 16`

   `x = 16 : 2`

   `x = 8`

   vậy `x = 8`

   `1-(12+3x)=7`

   ` 12 + 3x = 1 – 7 `

   `12 + 3x = -6`

   `3x = 12 – (-6)`

   `3x = 18`

   `x = 18 :3`

   `x = 6`

   vậy `x=6`

   `-(2x+2)+25=-19`

   `-(2x + 2 ) =  \-19 – 25`

   `-2x + 2  = -44`

   `-2x = – 44 – 2`

   `-2x = -46`

   `-x = – 46 : 2`

   `-x = -23`

   `x = -23`

   Vậy `x = – 23`

   `26-(26-x)=0`

   `26 – x = 26 – 0`

   `26 – x = 26`

   `x = 26 – 26`

   `x = 0`

   Vậy `x = 0`

   Xin hay nhất !!

    

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