1. Tim x: | |3x+1|-11 |=3. Cac ban giup minh nhe.Thank you cac ban nhieu Mong cac ban giai chi tiet voi a.

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1. `|3x+1||-11|=3`

   `⇔|3x+1|11=3`

   `⇔|3x+1|=3/11`

   ⇔\(\left[ \begin{array}{l}3x+1=\dfrac{3}{11}\\-(3x+1)=\dfrac{3}{11}\end{array} \right.\)⇔\(\left[ \begin{array}{l}x=-\dfrac{8}{33}\\x=-\dfrac{14}{33}\end{array} \right.\)

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2. $\text { Đáp án: }$

   $\text { | |3x + 1| – 11 | = 3 }$

   $\text { => |3x + 1| – 11 = 3 hoặc |3x + 1| – 11 = –3 }$

   $\text { TH1: |3x + 1| – 11 = 3 }$

   $\text { => |3x + 1| = 3 + 11 }$

   $\text { => |3x + 1| = 14 }$

   $\text { => 3x + 1 = 14 hoặc 3x + 1 = –14 }$

   $\text { => 3x = 14 – 1      | => 3x = –14 – 1 }$

   $\text { => 3x = 13            | => 3x = –15 }$

   $\text { => x = }$ $\frac {13}{3}$           $\text { | => x = –5 }$

   $\text { TH2: |3x + 1| – 11 = –3 }$

   $\text { => |3x + 1| = –3 + 11 }$

   $\text { => |3x + 1| = 8 }$

   $\text { => 3x + 1 = 8 hoặc 3x + 1 = –8 }$

   $\text { => 3x = 8 – 1      | => 3x = –8 – 1 }$

   $\text { => 3x = 7            | => 3x = –9 }$

   $\text { => x = }$ $\frac {7}{3}$            $\text { | => x = –3 }$

   $\text { Vậy x = }$ $\frac {13}{3}$ $ ; $ $\frac {7}{3}$ $ ; $ $\text {–5}$ $ ; $ $\text {–3}$ $.$ 

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