24 tháng 5 2022 lúc 20:36
\(-y^2-6y-9-\left(3x-5y\right)^2\ge0\)
\(\Leftrightarrow y^2+6y+9+\left(3x-5y\right)^2\ge0\)
\(\Leftrightarrow\left(y+3\right)^2+\left(3x-5y\right)^2\ge0\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(y+3\right)^2\ge0\\\left(3x-5y\right)^2\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y\ge-3\\3x+15\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y\ge-3\\x\ge-5\end{matrix}\right.\)
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