Ta có: \(\hept{\begin{cases}\left(3x-15\right)^2\ge0\forall x\\|-8-y|\ge0\forall x\end{cases}}\)
\(\Leftrightarrow\left(3x-15\right)^2+|-8-y|\ge0\forall x\)
\(\Leftrightarrow\left(3x-15\right)^2+|-8-y|+2020\ge2020\forall x\)
\(\Leftrightarrow A\ge2020\)
Dấu "=" xảy ra:
\(\Leftrightarrow\hept{\begin{cases}3x-15=0\\-8-y=0\end{cases}\Leftrightarrow\hept{\begin{cases}x=5\\y=-8\end{cases}}}\)
Vậy \(A_{Min}=2020\Leftrightarrow\hept{\begin{cases}x=5\\y=-8\end{cases}}\)