Question

4.x = 7.y và x\(^2\) + y\(^2\) = 260

Answer 1

\(4x=7y\Rightarrow\dfrac{x}{7}=\dfrac{y}{4}\)

Đặt \(\dfrac{x}{7}=\dfrac{y}{4}=k\Rightarrow x=7k;y=4k\)

\(x^2+y^2=260\\ \Rightarrow49k^2+16k^2=260\\ \Rightarrow65k^2=260\\ \Rightarrow k^2=4\\ \Rightarrow\left[{}\begin{matrix}k=2\\k=-2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=14;y=8\\x=-14;y=-8\end{matrix}\right.\)