Bài 10:
Đặt \(\dfrac{a}{5}=\dfrac{b}{4}=k\)
\(\Leftrightarrow\left\{{}\begin{matrix}a=5k\\b=4k\end{matrix}\right.\)
Ta có: \(a^2-b^2=36\)
\(\Leftrightarrow25k^2-16k^2=36\)
\(\Leftrightarrow k^2=4\)
Trường hợp 1: k=2
\(\Leftrightarrow\left\{{}\begin{matrix}a=5k=10\\b=4k=8\end{matrix}\right.\)
Trường hợp 2: k=-2
\(\Leftrightarrow\left\{{}\begin{matrix}a=5k=-10\\b=4k=-8\end{matrix}\right.\)