Question

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Answer 1

x= 4, y=10

 

Answer 2

x/y=2/5

=>x/2=y/5=xy/2.5=40/10=4

ta có x/2=4=>x=8

y/5=4=>y=20

Answer 3

Đặt \(\dfrac{x}{2}=\dfrac{y}{5}=k\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=2k\\y=5k\end{matrix}\right.\)

Ta có: xy=40

\(\Leftrightarrow10k^2=40\)

\(\Leftrightarrow k^2=4\)

Trường hợp 1: k=2

\(\Leftrightarrow\left\{{}\begin{matrix}x=2k=4\\y=5k=10\end{matrix}\right.\)

Trường hợp 2: k=-2

\(\Leftrightarrow\left\{{}\begin{matrix}x=2k=-4\\y=5k=-10\end{matrix}\right.\)