Tìm x: 1. -2.|x+3| + 1/2 = – 3/4 2. |x+1| – 5x = 3 3. |x-2| + 2|3+x| = 1

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1. Đáp án:

   1,x=-29/8

      x=-19/8

   2, x=-1/2

   3, x=-1

   Giải thích các bước giải:

   1,

   -2.|x+3| +1/2 =-3/4           

   -2.|x+3|=(-3/4)-1/2 

   -2.|x+3|=-5/4

   |x+3|=(-5/4):2

   |x+3|=-5/8

   TH1: x+3=-5/8

   x=(-5/8)-3

   x=-29/8

   TH2: x+3=5/8

   x=5/8 -3

   x=-19/8

   Vậy x=-29/8

          x=-19/8

   2,

   |x+1|-5x=3

   x+1-5x=3

   x-5x=3-1

   x-5x=2

   -4x=2

   x=2:-4

   x=-1/2

   Vậy x=-1/2

   3, |x-2|+2|3+x| =1

   x-2 + 2.3+2x=1

   x-2+6+2x=1

   x-2+2x=-5 

   x+2x=(-5)+2

   x+2x=-3

   3x=-3

   x=-1   

   Vậy x=-1   

    

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2. Đáp án:

   $a)$ \(\left[ \begin{array}{l}x=\dfrac{-29}{8}\\x=\dfrac{-19}{8}\end{array} \right.\) 

   $b) x=\dfrac{-1}{2}$

   $c) x=-1$

   Giải thích các bước giải:

    Bài $1:$

   $a) -2×|x+3|+\dfrac{1}{2}=\dfrac{-3}{4}$

   $⇒|x+3|=(\dfrac{-3}{4}-\dfrac{1}{2})÷2$

   $⇒|x+3|=\dfrac{-5}{8}$

   $+) |x+3|=\dfrac{5}{8}$

   $⇒x+3=\dfrac{5}{8}$

   $⇒x=\dfrac{5}{8}-3$

   $⇒x=\dfrac{-19}{8}$

   $+) |x+3|=\dfrac{-5}{8}$

   $⇒x+3=\dfrac{-5}{8}$

   $⇒x=\dfrac{-5}{8}-3$

   $⇒x=\dfrac{-29}{8}$

   Vậy \(\left[ \begin{array}{l}x=\dfrac{-19}{8}\\x=\dfrac{-29}{8}\end{array} \right.\) 

   $b) |x+1|-5x=3$

   $⇒x+1-5x=3$

   $⇒-4x=3-1$

   $⇒-4x=2$

   $⇒x=\dfrac{-1}{2}$

   $c) |x-2|+2|3+x|=1$

   $⇒x-2+6+2x=1$

   $⇒x+2x=1+2-6$

   $⇒3x=-3$

   $⇒x=-1$

   Xin hay nhất 

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