Làm giúp mình nha , mìn cảm ơn nhiều lắm nha

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Làm giúp mình nha , mìn cảm ơn nhiều lắm nha
lam-giup-minh-nha-min-cam-on-nhieu-lam-nha

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Gerda 1 year 2020-10-21T23:45:00+00:00 1 Answers 67 views 0

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    2020-10-21T23:46:26+00:00

    Đáp án:

    7) \(\left\{ \begin{array}{l}
    y = 8\\
    x = 12\\
    z = 6
    \end{array} \right.\)

    Giải thích các bước giải:

    \(\begin{array}{l}
    2)\left\{ \begin{array}{l}
    x = \dfrac{9}{8}y\\
    z = \dfrac{9}{{12}}y = \dfrac{3}{4}y\\
    \dfrac{9}{8}y + y + \dfrac{3}{4}y = 69
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    x = \dfrac{9}{8}y\\
    z = \dfrac{3}{4}y\\
    \left( {\dfrac{9}{8} + 1 + \dfrac{3}{4}} \right)y = 69
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    x = \dfrac{9}{8}y\\
    z = \dfrac{3}{4}y\\
    \dfrac{{23}}{8}y = 69
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    y = 24\\
    x = 27\\
    z = 18
    \end{array} \right.\\
    4)\left\{ \begin{array}{l}
    x = \dfrac{3}{8}y\\
    z = \dfrac{5}{8}y\\
    4.\dfrac{3}{8}y + 3y – 2.\dfrac{5}{8}y = 78
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    x = \dfrac{3}{8}y\\
    z = \dfrac{5}{8}y\\
    \dfrac{{13}}{4}y = 78
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    y = 24\\
    x = 9\\
    z = 15
    \end{array} \right.\\
    6)\left\{ \begin{array}{l}
    x = \dfrac{4}{5}y\\
    z = \dfrac{2}{5}y\\
    \dfrac{4}{5}y + y – \dfrac{2}{5}y = 21
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    \dfrac{7}{5}y = 21\\
    x = \dfrac{4}{5}y\\
    z = \dfrac{2}{5}y
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    y = 15\\
    x = 12\\
    z = 6
    \end{array} \right.\\
    7)\left\{ \begin{array}{l}
    x = 4 + y\\
    4\left( {4 + y} \right) = 6y\\
    z = \dfrac{6}{8}y
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    2y = 16\\
    x = 4 + y\\
    z = \dfrac{6}{8}y
    \end{array} \right.\\
     \to \left\{ \begin{array}{l}
    y = 8\\
    x = 12\\
    z = 6
    \end{array} \right.
    \end{array}\)

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