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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 9: Giai hpt sau: $\left \{{{|x|+3y=7} \atop {2x+2|y-1|=3}} \right.$

Tháng Hai 20, 2023 Toán học 1 Comment 0 views

Toán Lớp 9: Giai hpt sau:
$\left \{{{|x|+3y=7} \atop {2x+2|y-1|=3}} \right.$

Comments ( 1 )

  1. dinhcongson
    dinhcongson
    20 Tháng Hai, 2023 at 10:44 chiều
    Reply
    $\begin{array}{l} \left\{ \begin{array}{l} \left| x \right| + 3y = 7\\ 2x + 2\left| {y – 1} \right| = 3 \end{array} \right.\\  + x \ge 0,y \ge 1\\  \Leftrightarrow \left\{ \begin{array}{l} x + 3y = 7\\ 2x + 2y – 2 = 3 \end{array} \right.\\  \Leftrightarrow \left\{ \begin{array}{l} x + 3y = 7\\ 2x + 2y = 5 \end{array} \right.\\  \Leftrightarrow \left\{ \begin{array}{l} x = \dfrac{1}{4}\\ y = \dfrac{9}{4} \end{array} \right.(TM)\\  + x < 0,y < 1\\ \left\{ \begin{array}{l}  – x + 3y = 7\\ 2x + 2\left( {1 – y} \right) = 3 \end{array} \right.\\  \Leftrightarrow \left\{ \begin{array}{l}  – x + 3y = 7\\ 2x – 2y = 1 \end{array} \right.\\  \Leftrightarrow \left\{ \begin{array}{l} x = \dfrac{{17}}{4}\\ y = \dfrac{{15}}{4} \end{array} \right.(L)\\ x \ge 0,y < 1\\ \left\{ \begin{array}{l} x + 3y = 7\\ 2x + 2\left( {1 – y} \right) = 3 \end{array} \right.\\  \Leftrightarrow \left\{ \begin{array}{l} x + 3y = 7\\ 2x – 2y = 1 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l} x = \dfrac{{17}}{8}\\ y = \dfrac{{13}}{8} \end{array} \right.(L)\\ x < 0,y \ge 1\\ \left\{ \begin{array}{l}  – x + 3y = 7\\ 2x + 2\left( {y – 1} \right) = 3 \end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}  – x + 3y = 7\\ 2x + 2y = 5 \end{array} \right.\\  \Leftrightarrow \left\{ \begin{array}{l} x = \dfrac{1}{8}\\ y = \dfrac{{19}}{8} \end{array} \right.(L)\\  \to \left( {x;y} \right) = \left( {\dfrac{1}{4};\dfrac{9}{4}} \right) \end{array}$  

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222-9+11+12:2*14+14 = ? ( )

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