Ta có:\(\left\{{}\begin{matrix}\dfrac{x}{2}=\dfrac{y}{3}\Rightarrow\dfrac{x}{10}=\dfrac{y}{15}\\\dfrac{y}{5}=\dfrac{z}{7}\Rightarrow\dfrac{y}{15}=\dfrac{z}{21}\end{matrix}\right.\Rightarrow\dfrac{x}{10}=\dfrac{y}{15}=\dfrac{z}{21}\)
Áp dụng tính chất cảu dãy tỉ số bằng nhau ta có:
\(\dfrac{x}{10}=\dfrac{y}{15}=\dfrac{z}{21}=\dfrac{x+y+z}{10+15+21}=\dfrac{921}{46}\)
\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{921}{46}.10=\dfrac{4605}{23}\\y=\dfrac{921}{46}.15=\dfrac{13815}{46}\\z=\dfrac{921}{46}.21=\dfrac{19341}{46}\end{matrix}\right.\)
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