Tìm x, biết -3/5.x=1/4+0,75 c) (1/7−1/3).x=28/3.(1/4−1/7) d) 5/7.x=9/8−0,125 e)(2/11+1/3).x=(1/7−1/8).5/6

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1. Đáp án:

    BẠN THAM KHẢO NHA!

   Giải thích các bước giải:

    $a, \dfrac{-3}{5}.x=\dfrac{1}{4}+0,75$

   $=> \dfrac{-3}{5}.x=1$

   $=> x=-1.\dfrac{5}{3}=-\dfrac{5}{3}$

   $b, (\dfrac{1}{7}-\dfrac{1}{3}).x=\dfrac{28}{3}.(\dfrac{1}{4}-\dfrac{1}{7})$

   $=> x=-1.\dfrac{21}{4}=-\dfrac{21}{4}$

   $c, \dfrac{5}{7}x=\dfrac{9}{8}-0,125$

   $=> \dfrac{5}{7}x=1$

   $=> x=\dfrac{7}{5}$

   $d, (\dfrac{2}{11}+\dfrac{1}{3})x=(\dfrac{1}{7}-\dfrac{1}{8}).\dfrac{5}{6}$

   $=> \dfrac{17}{33}x=\dfrac{5}{336}$

   $=> x=\dfrac{55}{1904}$

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2. a,  $\frac{-3}{5}$x = $\frac{1}{4}$ + 0,75  

   ⇔$\frac{-3}{5}$x = $\frac{1}{4}$ + $\frac{3}{4}$ 

   ⇔$\frac{-3}{5}$x = 1

   ⇔x = 1: $\frac{-3}{5}$ 

   ⇔x = $\frac{-5}{3}$ 

   KL: x = $\frac{-5}{3}$ 

   c, ($\frac{1}{7}$ – $\frac{1}{2}$)x = $\frac{28}{3}$( $\frac{1}{4}$ – $\frac{1}{7}$ 

   ⇔$\frac{-4}{21}$x = $\frac{28}{3}$. $\frac{3}{28}$

   ⇔$\frac{-4}{21}$x = 1

   ⇔x = 1 : $\frac{-4}{21}$ 

   ⇔x = $\frac{-21}{4}$ 

   KL: ….

   d, $\frac{5}{7}$x = $\frac{9}{8}$ – 0,125

   ⇔$\frac{5}{7}$x = $\frac{9}{8}$ – $\frac{1}{8}$ 

   ⇔$\frac{5}{7}$x = 1 

   ⇔x = $\frac{7}{5}$ 

   KL: ….

   e, ($\frac{2}{11}$ + $\frac{1}{3}$)x = ( $\frac{1}{7}$ – $\frac{1}{8}$) $\frac{5}{6}$ 

   ⇔$\frac{17}{33}$x = $\frac{5}{336}$

   ⇔x = $\frac{55}{1904}$ 

   KL: ….

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