a,12-|x+2|=10 b,1/2.x+150%x=2020 c,-5/4-x=1/16 d,(3/7.x+1)÷(-4)=-1/28

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1. Đáp án + Giải thích các bước giải:

    `a,`

   `12 – |x + 2| = 10`

   `⇒|x + 2| = 12 – 10`

   `⇒|x + 2|  =2`

   `⇒`\(\left[ \begin{array}{l}x + 2 = 2\\x + 2 = -2\end{array} \right.\) 

   `⇒` \(\left[ \begin{array}{l}x=0\\x=-4\end{array} \right.\) 

   `b,`

       `1/2 . x + 150%x = 2020`

   `⇒ 1/2 . x  + 3/2.x=  2020`

   `⇒x . (1/2 + 3/2) = 2020`

   `⇒x .  2 = 2020`

   `⇒x = 2020 ÷ 2`

   `⇒x = 1010`

   `c,`

   `(-5)/4 – x = 1/16`

   `⇒x = (-5)/4 – 1/16`

   `⇒x = (-20)/16 – 1/16`

   `⇒x = (-21)/16`

   `d,`

   `(3/7 . x + 1) ÷ (-4)  = (-1)/28`

   `⇒3/7 .x  + 1=  (-1)/28 . (-4)`

   `⇒3/7.x + 1 = 1/7`

   `⇒3/7.x = 1/7 –  1`

   `⇒3/7.x = 1/7 – 7/7`

   `⇒3/7.x = (-6)/7`

   `⇒x = (-6)/7 : 3/7`

   `⇒x  = (-6)/7 . 7/3`

   `⇒x = – 2`

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2. `a, 12 – |x+2|=10`

   `⇒ |x+2|=2`

   \(⇒ \left[ \begin{array}{l}x+2=2\\x+2=-2\end{array} \right.\)

   \(⇒ \left[ \begin{array}{l}x=0\\x=-4\end{array} \right.\)

   $\text{Vậy x ∈ {0; -4}}$

   `b, 1/2 x + 150%x = 2020`

   `⇒ 0,5x + 1,5x = 2020`

   `⇒ (0,5+1,5)x=2020`

   `⇒ 2x=2020`

   `⇒ x = 1010`

   `c, (-5)/4 – x = 1/16`

   `⇒ x = (-5)/4 – 1/16`

   `⇒ x = (-20)/16 – 1/16`

   `⇒ x = -21/16`

   `d, (3/7 x + 1):(-4)=(-1)/28`

   `⇒ 3/7 x + 1 = (-1)/28 . (-4)`

   `⇒ 3/7 x + 1 = 1/7`

   `⇒ 3/7 x = (-6)/7`

   `⇒ x = (-6)/7 : 3/7`

   `⇒ x = (-6)/7 . 7/3`

   `⇒ x=-2`

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