Câu hỏi của Sương Đặng - Toán lớp 7 | Học trực tuyến - Hoc24.vn
\(3x=4y;5y=6z\)
\(\Rightarrow\dfrac{x}{4}=\dfrac{y}{3};\dfrac{y}{6}=\dfrac{z}{5}\)
\(\Rightarrow\dfrac{x}{8}=\dfrac{y}{6};\dfrac{y}{6}=\dfrac{z}{5}\)
\(\Rightarrow\dfrac{x}{8}=\dfrac{y}{6}=\dfrac{z}{5}\)
Đặt:
\(\dfrac{x}{8}=\dfrac{y}{6}=\dfrac{z}{5}=k\)
\(\Rightarrow\left\{{}\begin{matrix}x=8k\\y=6k\\z=5k\end{matrix}\right.\)
\(\Rightarrow8k.6k.5k=30\)
\(\Rightarrow240k^3=30\)
\(k^3=\dfrac{1}{8}\)
\(k=\dfrac{1}{2}\)
\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{1}{2}.8=4\\y=\dfrac{1}{2}.6=3\\z=\dfrac{1}{2}.5=2,5\end{matrix}\right.\)
