Bài 1 : a) 7/5 – 2/5 x = 1 – 3/20 b) 2/5 x + -3/7 = -1/5 ,x + 8/14 Bài 2 : a) (-4) – 2x = (-3).6 b ) -3/4 . / x -5 / = -9/2

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1. Đáp án:

    $1)
   a)x=\dfrac{11}{8}\\
   b)
    x=\dfrac{5}{3}\\
   2)
   a) x=7\\
   b){\left[\begin{aligned}x=11\\x=-1\end{aligned}\right.}\\$

   Giải thích các bước giải:

    $1)
   a)\dfrac{7}{5}-\dfrac{2}{5}x=1-\dfrac{3}{20}\\
   \Leftrightarrow \dfrac{2}{5}x=\dfrac{7}{5}-1+\dfrac{3}{20}\\
   \Leftrightarrow \dfrac{2}{5}x=\dfrac{28}{20}-\dfrac{20}{20}+\dfrac{3}{20}\\
   \Leftrightarrow \dfrac{2}{5}x=\dfrac{11}{20}\\
   \Leftrightarrow x=\dfrac{11}{20}.\dfrac{5}{2}=\dfrac{11}{8}\\
   b)
   \dfrac{2}{5}x+\dfrac{-3}{7}=\dfrac{-1}{5}x+\dfrac{8}{14}\\
   \Leftrightarrow \dfrac{2}{5}x+\dfrac{1}{5}x=\dfrac{8}{14}+\dfrac{3}{7}\\
   \Leftrightarrow \dfrac{2}{5}x+\dfrac{1}{5}x=\dfrac{4}{7}+\dfrac{3}{7}\\
   \Leftrightarrow \dfrac{3}{5}x=\dfrac{7}{7}=1\\
   \Leftrightarrow x=\dfrac{5}{3}\\
   2)
   a)(-4)-2x=(-3).6\\
   \Leftrightarrow 2x=-4+18=14\\
   \Leftrightarrow x=7\\
   b)\dfrac{-3}{4}.|x-5|=\dfrac{-9}{2}\\
   \Leftrightarrow |x-5|=\dfrac{-9}{2}.\dfrac{-4}{3}=6\\
   \Leftrightarrow {\left[\begin{aligned}x-5=6\\x-5=-6\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned}x=11\\x=-1\end{aligned}\right.}\\$

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