Bài 1 a) `1/12 x – 75%x = -1 2/3` b)` (4,5 -2x . (-1 4/7) = 11/14 c) `-2/3 x – 4/7 = 1/14` d) `(-2x/5 + 1 ) : (-5) = -1/25

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1. Đáp án:

    $a) 
   x=\dfrac{5}{2}\\
   b)
   x=\dfrac{-13}{11}\\
   c)
   x=\dfrac{-27}{28}\\
   d)
   x=2\\$

   Giải thích các bước giải:

    $a) 
   \dfrac{1}{12}x-\dfrac{75}{100}x=-1\dfrac{2}{3}\\
   \Leftrightarrow \dfrac{1}{12}x-\dfrac{3}{4}x=\dfrac{-5}{3}\\
   \Leftrightarrow \dfrac{1}{12}x-\dfrac{9}{12}x=\dfrac{-5}{3}\\
   \Leftrightarrow \dfrac{-8}{12}x=\dfrac{-5}{3}\\
   \Leftrightarrow \dfrac{-2}{3}x=\dfrac{-5}{3}\\
   \Leftrightarrow x=\dfrac{-5}{3}.\dfrac{-3}{2}=\dfrac{5}{2}\\
   b)
   4,5-2x.\left ( -1\dfrac{4}{7} \right )=\dfrac{11}{14}\\
   \Leftrightarrow \dfrac{9}{2}-2x.\dfrac{-11}{7}=\dfrac{11}{14}\\
   \Leftrightarrow \dfrac{22}{7}x=\dfrac{11}{14}-\dfrac{9}{2}\\
   \Leftrightarrow \dfrac{22}{7}x=\dfrac{11}{14}-\dfrac{9.7}{14}\\
   \Leftrightarrow \dfrac{22}{7}x=\dfrac{-52}{14}=\dfrac{-26}{7}\\
   \Leftrightarrow x=\dfrac{-26}{7}.\dfrac{7}{22}=\dfrac{-13}{11}\\
   c)
   -\dfrac{2}{3}x-\dfrac{4}{7}=\dfrac{1}{14}\\
   \Leftrightarrow -\dfrac{2}{3}x=\dfrac{4}{7}+\dfrac{1}{14}\\
   \Leftrightarrow \dfrac{-2}{3}x=\dfrac{8}{14}+\dfrac{1}{14}\\
   \Leftrightarrow \dfrac{-2}{3}x=\dfrac{9}{14}\\
   \Leftrightarrow x=\dfrac{9}{14}.\dfrac{-3}{2}=\dfrac{-27}{28}\\
   d)
   \left ( \dfrac{-2x}{5}+1 \right ):(-5)=\dfrac{-1}{25}\\
   \Leftrightarrow \dfrac{-2x}{5}+1 =\dfrac{-1}{25}.(-5)=\dfrac{1}{5}\\
   \Leftrightarrow \dfrac{-2x}{5}=\dfrac{1}{5}-1\\
   \Leftrightarrow \dfrac{-2x}{5}=\dfrac{1}{5}-\dfrac{5}{5}=\dfrac{-4}{5}\\
   \Leftrightarrow x=\dfrac{-4}{5}.\dfrac{-5}{2}=2\\$

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