Tìm x A) 3 1/2 – 4/2x = 2/3 B) (x +1/2).(2/3-2x) = 0 C) 3/4 – |2x – 2/3| = -4/7

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1. Đáp án: a.$ x=\dfrac{12}{17}$

                b.$x\in\{-\dfrac12,\dfrac13\}$

                c.$x\in\{-\dfrac{55}{168},\dfrac{167}{168}\}$

   Giải thích các bước giải:

    a.Ta có:

   $3\dfrac12-\dfrac4{2x}=\dfrac23$

   $\to \dfrac{3\cdot 2+1}2-\dfrac2{x}=\dfrac23$

   $\to \dfrac{7}2-\dfrac2{x}=\dfrac23$

   $\to \dfrac2{x}=\dfrac{7}2-\dfrac23$

   $\to \dfrac2{x}=\dfrac{17}6$

   $\to x=\dfrac{2\cdot 6}{17}$

   $\to x=\dfrac{12}{17}$

   b.Ta có:

   $(x+\dfrac12)(\dfrac23-2x)=0$

   $\to x+\dfrac12=0\to x=-\dfrac12$

   Hoặc $\dfrac23-2x=0\to 2x=\dfrac23\to x=\dfrac13$

   c.Ta có:

   $\dfrac34-|2x-\dfrac23|=-\dfrac47$

   $\to |2x-\dfrac23|=\dfrac34+\dfrac47$

   $\to |2x-\dfrac23|=\dfrac{37}{28}$

   $\to 2x-\dfrac23=\dfrac{37}{28}$

   $\to 2x=\dfrac23+\dfrac{37}{28}$

   $\to 2x=\dfrac{167}{84}$

   $\to x=\dfrac{167}{168}$

   Hoặc $2x-\dfrac23=-\dfrac{37}{28}$

   $\to 2x=\dfrac23-\dfrac{37}{28}$

   $\to 2x=-\dfrac{55}{84}$

   $\to x=-\dfrac{55}{168}$

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