Bài 1: a) 7/5 – 2/5 x = 1 – 3/20 b) 2/5 x + -3/7 = -1/5 x + 8/14 c) / 3/2 – x / = 25% Bài 2 : a) x + 2/5 = -7/10 b) (-4)-2x = (-3).6 c) 2/3 – ( 8/3

0 bình luận về “Bài 1: a) 7/5 – 2/5 x = 1 – 3/20 b) 2/5 x + -3/7 = -1/5 x + 8/14 c) / 3/2 – x / = 25% Bài 2 : a) x + 2/5 = -7/10 b) (-4)-2x = (-3).6 c) 2/3 – ( 8/3”

1. Đáp án:

    $1)
   a)x=\dfrac{11}{8}\\
   b)
   x=\dfrac{5}{3}\\
   c)
    {\left[\begin{aligned} x =\dfrac{5}{4}\\ x =\dfrac{7}{4}\end{aligned}\right.}\\
   2)
   a)
   x=\dfrac{-11}{10}\\
   b)
   x=7\\
   c)
    x=1\\
   d)
   {\left[\begin{aligned}x=11\\x=-1\end{aligned}\right.}\\$

   Giải thích các bước giải:

    $1)
   a)\dfrac{7}{5}-\dfrac{2}{5}x=1-\dfrac{3}{20}\\
   \Leftrightarrow \dfrac{2}{5}x=\dfrac{7}{5}-1+\dfrac{3}{20}\\
   \Leftrightarrow \dfrac{2}{5}x=\dfrac{28}{20}-\dfrac{20}{20}+\dfrac{3}{20}\\
   \Leftrightarrow \dfrac{2}{5}x=\dfrac{11}{20}\\
   \Leftrightarrow x=\dfrac{11}{20}.\dfrac{5}{2}=\dfrac{11}{8}\\
   b)
   \dfrac{2}{5}x+\dfrac{-3}{7}=\dfrac{-1}{5}x+\dfrac{8}{14}\\
   \Leftrightarrow \dfrac{2}{5}x+\dfrac{1}{5}x=\dfrac{3}{7}+\dfrac{8}{14}\\
   \Leftrightarrow \dfrac{3}{5}x=\dfrac{6}{14}+\dfrac{8}{14}=\dfrac{14}{14}\\
   \Leftrightarrow x=1.\dfrac{5}{3}=\dfrac{5}{3}\\
   c)
   \left | \dfrac{3}{2}-x \right |=\dfrac{25}{100}=\dfrac{1}{4}\\
   \Leftrightarrow {\left[\begin{aligned} \dfrac{3}{2}-x =\dfrac{1}{4}\\ \dfrac{3}{2}-x =-\dfrac{1}{4}\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned} x =\dfrac{3}{2}-\dfrac{1}{4}\\ x =\dfrac{3}{2}+\dfrac{1}{4}\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned} x =\dfrac{6}{4}-\dfrac{1}{4}\\ x =\dfrac{6}{4}+\dfrac{1}{4}\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned} x =\dfrac{5}{4}\\ x =\dfrac{7}{4}\end{aligned}\right.}\\
   2)
   a)
   x+\dfrac{2}{5}=-\dfrac{7}{10}\\
   \Leftrightarrow x=\dfrac{-7}{10}-\dfrac{2}{5}\\
   \Leftrightarrow x=\dfrac{-7}{10}-\dfrac{4}{10}\\
   \Leftrightarrow x=\dfrac{-11}{10}\\
   b)
   (-4)-2x=(-3).6\\
   \Leftrightarrow 2x=-4+18=14\\
   \Leftrightarrow x=7\\
   c)
   \dfrac{2}{3}-\left ( \dfrac{8}{3}-x \right )=-1\\
   \Leftrightarrow \dfrac{2}{3}-\dfrac{8}{3}+x =-1\\
   \Leftrightarrow \dfrac{-6}{3}+x=-1\\
   \Leftrightarrow x=-1+2\\
   \Leftrightarrow x=1\\
   d)
   \dfrac{-3}{4}.\left | x-5 \right |=\dfrac{-9}{2}\\
   \Leftrightarrow \left | x-5 \right |=\dfrac{-9}{2}.\dfrac{-4}{3}\\
   \Leftrightarrow \left | x-5 \right |=6\\
   \Leftrightarrow {\left[\begin{aligned}x-5=6\\x-5=-6\end{aligned}\right.}\\
   \Leftrightarrow {\left[\begin{aligned}x=11\\x=-1\end{aligned}\right.}\\$

   Bình luận