\(\Rightarrow\dfrac{x}{4}=\dfrac{y}{5}\) và \(2y-x=3\)
\(\dfrac{x}{4}=\dfrac{y}{5}\Rightarrow\dfrac{2y-x}{2.5-4}=\dfrac{3}{6}=\dfrac{1}{2}\)
\(\dfrac{x}{4}=\dfrac{1}{2}\Rightarrow x=\dfrac{1}{2}.4=2\)
\(\dfrac{y}{5}=\dfrac{1}{2}\Rightarrow y=\dfrac{1}{2}.5=\dfrac{5}{2}=2,5\)
\(5x=4y\Leftrightarrow\dfrac{x}{4}=\dfrac{y}{5}\)
\(\Leftrightarrow\dfrac{x}{4}=\dfrac{2y}{25}\)
Áp dụng t/c dãy tỉ số bằng nhau ta có :
\(\dfrac{x}{4}=\dfrac{2y}{25}=\dfrac{2y-x}{25-4}=\dfrac{3}{21}=\dfrac{1}{7}\)
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{x}{4}=\dfrac{1}{7}\\\dfrac{2y}{25}=\dfrac{1}{7}\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{4}{7}\\y=\dfrac{25}{14}\end{matrix}\right.\)
Vậy ......
