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\(x^2-4x+9y^2+6y+10\\ =\left(x^2-4x+4\right)+\left(9y^2+6y+1\right)+5\\ =\left(x-2\right)^2+\left(3y+1\right)^2+5\ge5>0\)
\(a,4x^2+9y^2+4x-24y+17=0\)
\(\Rightarrow\left(4x^2+4x+1\right)+\left(9y^2-24y+16\right)=0\)
\(\Rightarrow\left(2x+1\right)^2+\left(3y-4\right)^2=0\)
\(\left(2x+1\right)^2\ge0;\left(3y-4\right)^2\ge0\)
\(\Rightarrow\hept{\begin{cases}\left(2x+1\right)^2=0\\\left(3y-4\right)^2=0\end{cases}\Rightarrow\hept{\begin{cases}2x+1=0\\3y-4=0\end{cases}\Rightarrow}\hept{\begin{cases}x=-\frac{1}{2}\\y=\frac{4}{3}\end{cases}}}\)
\(pt\Leftrightarrow\left(x+1\right)^2+\left(3y-1\right)^2=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}x+1=0\\3y-1=0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=-1\\y=\frac{1}{3}\end{matrix}\right.\)
Vậy...
\(x^2+2x+9y^2+6y+15\)
\(=\left(x^2+2x+1\right)+\left(9y^2+6y+1\right)+13\)
\(=\left(x+1\right)^2+\left(3y+1\right)^2+13\ge13>0\)
\(x^2+9y^2+2x-6y+2=0\)
\(\Leftrightarrow x^2+2x+1+9y^2-6y+1=0\)
\(\Leftrightarrow\left(x+1\right)^2+\left(3y-1\right)^2=0\)
Đẳng thức xảy ra khi \(x=-1;y=\frac{1}{3}\)