(-3)+8x=6x+20 6+8x=6x+20 3.(x+1)+5.(x+2)=21 9.(x+5)-4x-40=10

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1. `\text{~~Holi~~}`

   `a. (-3)+8x=6x+20`

   `-> -3+8x=6x+20`

   `-> 8x-6x=20+3`

   `-> 2x=23`

   `-> x=(23)/2`

   `b. 6+8x=6x+20`

   `-> 8x-6x=20-6`

   `-> 2x=14`

   `-> x=7`

   `c. 3(x+1)+5(x+2)=21`

   `-> 3x+4+5x+10=21`

   `-> 8x+13=21`

   `-> 8x=21-13`

   `-> 8x=8`

   `-> x=1`

   `d. 9(x+5)-4x-40=10`

   `-> 9x+45-4x-40=10`

   `-> 5x+5=10`

   `-> x=1`

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2. Đáp án:

    d) x=1

   Giải thích các bước giải:

   \(\begin{array}{l}
   a) – 3 + 8x = 6x + 20\\
    \to 2x = 23\\
    \to x = \dfrac{{23}}{2}\\
   b)6 + 8x = 6x + 20\\
    \to 2x = 14\\
    \to x = 7\\
   c)3\left( {x + 1} \right) + 5\left( {x + 2} \right) = 21\\
    \to 3x + 3 + 5x + 10 = 21\\
    \to 8x = 8\\
    \to x = 1\\
   d)9\left( {x + 5} \right) – 4x – 40 = 10\\
    \to 9x + 45 – 4x – 40 = 10\\
    \to 5x = 5\\
    \to x = 1
   \end{array}\)

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