Toán Lớp 7: Tìm x, y, z biết: 7/3x = 2/16y = 19/6z ; 2x-y-z=-6
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Toán Lớp 7: Tìm x, y, z biết: 7/3x = 2/16y = 19/6z ; 2x-y-z=-6
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\dfrac{7}{3}x = \dfrac{2}{{16}}y = \dfrac{{19}}{6}z\\
\Leftrightarrow \dfrac{7}{3}x = \dfrac{1}{8}y = \dfrac{{19}}{6}z\\
\Leftrightarrow \dfrac{{7x}}{{3.7.19}} = \dfrac{y}{{8.7.19}} = \dfrac{{19z}}{{6.7.19}}\\
\Leftrightarrow \dfrac{x}{{57}} = \dfrac{y}{{1064}} = \dfrac{z}{{42}} = \dfrac{{2x}}{{114}}\\
= \dfrac{{2x – y – z}}{{114 – 1064 – 42}} = \dfrac{{ – 6}}{{ – 992}} = \dfrac{3}{{496}}\\
\Leftrightarrow \left\{ \begin{array}{l}
x = \dfrac{3}{{496}}.57 = \dfrac{{171}}{{496}}\\
y = \dfrac{3}{{496}}.1064 = \dfrac{{399}}{{62}}\\
z = \dfrac{3}{{496}}.42 = \dfrac{{63}}{{248}}
\end{array} \right.\\
Vậy\,x = \dfrac{{171}}{{496}};y = \dfrac{{399}}{{62}};z = \dfrac{{63}}{{248}}
\end{array}$