Tìm x,y,z biết 4x-2/7=5y-7/3=4x-5y+5/2x

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Tìm x,y,z biết 4x-2/7=5y-7/3=4x-5y+5/2x

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Neala 5 years 2021-05-18T09:12:01+00:00 1 Answers 19 views 0

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  1. Edana
    0
    2021-05-18T09:13:53+00:00
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    Giải thích các bước giải:

     Ta có:

    $\begin{array}{l}
    \dfrac{{4x – 2}}{7} = \dfrac{{5y – 7}}{3} = \dfrac{{4x – 5y + 5}}{{2x}}\\
     \Leftrightarrow \left\{ \begin{array}{l}
    \dfrac{{4x – 2}}{7} = \dfrac{{5y – 7}}{3} = \dfrac{{4x – 5y + 5}}{{7 – 3}} = \dfrac{{4x – 5y + 5}}{4}\\
    \dfrac{{4x – 2}}{7} = \dfrac{{5y – 7}}{3} = \dfrac{{4x – 5y + 5}}{{2x}}
    \end{array} \right.\\
     \Rightarrow \dfrac{{4x – 5y + 5}}{4} = \dfrac{{4x – 5y + 5}}{{2x}}\\
     \Leftrightarrow \left[ \begin{array}{l}
    4x – 5y + 5 = 0\\
    2x = 4
    \end{array} \right.\\
     \Leftrightarrow \left[ \begin{array}{l}
    4x – 2 = 5y – 7 = 0\\
    x = 2
    \end{array} \right.\\
     \Leftrightarrow \left[ \begin{array}{l}
    x = \dfrac{1}{2};y = \dfrac{7}{5}\\
    x = 2;\dfrac{{5y – 7}}{3} = \dfrac{{4.2 – 2}}{7}
    \end{array} \right.\\
     \Leftrightarrow \left[ \begin{array}{l}
    x = \dfrac{1}{2};y = \dfrac{7}{5}\\
    x = 2;y = \dfrac{{67}}{{35}}
    \end{array} \right.
    \end{array}$

    Vậy $\left( {x;y} \right) = \left\{ {\left( {\dfrac{1}{2};\dfrac{7}{5}} \right);\left( {2;\dfrac{{67}}{{35}}} \right)} \right\}$

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )