\(\dfrac{x}{3}=\dfrac{y}{4}\Leftrightarrow\left(\dfrac{x}{3}\right)^2=\left(\dfrac{y}{4}\right)^2\Leftrightarrow\dfrac{x^2}{9}=\dfrac{y^2}{16}\)
Áp dụng tính chất dãy tỉ số bằng nhau ta có:
\(\dfrac{x^2}{9}=\dfrac{y^2}{16}=\dfrac{x^2+y^2}{9+16}=\dfrac{25}{25}=1\)
\(\Rightarrow\left\{{}\begin{matrix}x^2=1.9=9\\y^2=1.16=16\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\pm3\\y=\pm4\end{matrix}\right.\)
