Question

Tìm x,y,z biết :

Answer 1

Ai biết câu nào giúp mik câu đó với , cảm ơn !!!

Answer 2

\(1,\dfrac{x}{-3}=\dfrac{y}{8}\Leftrightarrow\dfrac{x^2}{9}=\dfrac{y^2}{64}=\dfrac{x^2-y^2}{9-64}=\dfrac{\dfrac{-44}{5}}{-55}=\dfrac{4}{25}\\ \Leftrightarrow\left\{{}\begin{matrix}x^2=\dfrac{36}{25}\\y^2=\dfrac{256}{25}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\pm\dfrac{6}{5}\\y=\pm\dfrac{16}{5}\end{matrix}\right.\)

\(2,\dfrac{x}{5}=\dfrac{y}{-4}=\dfrac{z}{6}=k\Leftrightarrow x=5k;y=-4k;z=6k\\ xyz=15\Leftrightarrow-120k^3=15\Leftrightarrow k^3=-\dfrac{1}{8}\\ \Leftrightarrow k=-\dfrac{1}{2}\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{5}{2}\\y=2\\z=-3\end{matrix}\right.\)

\(3,5x=8y=3z\Leftrightarrow\dfrac{x}{\dfrac{1}{5}}=\dfrac{y}{\dfrac{1}{8}}=\dfrac{z}{\dfrac{1}{3}}=\dfrac{x-2y+z}{\dfrac{1}{5}-\dfrac{1}{8}\cdot2+\dfrac{1}{3}}=\dfrac{34}{\dfrac{17}{60}}=120\\ \Leftrightarrow\left\{{}\begin{matrix}x=120\cdot\dfrac{1}{5}=24\\y=120\cdot\dfrac{1}{8}=15\\z=120\cdot\dfrac{1}{3}=40\end{matrix}\right.\)