Question

tìm x,y biết x/3=y/4 và x.y=108

Answer 1

\(\dfrac{x}{3}=\dfrac{y}{4}=k\)

\(\Rightarrow\left\{{}\begin{matrix}x=3k\\y=4k\end{matrix}\right.\)

\(\Rightarrow xy=12k^2=108\Rightarrow k=\pm3\)

\(\Rightarrow\left\{{}\begin{matrix}x=\pm9\\y=\pm12\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=9\\y=12\end{matrix}\right.\\\left\{{}\begin{matrix}x=-9\\y=-12\end{matrix}\right.\end{matrix}\right.\)