a/ Với mọi x, y ta có :
\(\left\{{}\begin{matrix}\left|x-2\right|\ge0\\y^2\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left|x-2\right|+y^2\ge0\)
\(\Leftrightarrow\left|x-2\right|+y^2+5\ge5\)
\(\Leftrightarrow A\ge5\)
Dấu "=" xảy ra khi :
\(\left\{{}\begin{matrix}\left|x-2\right|=0\\y^2=0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=0\end{matrix}\right.\)
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b/ Với mọi x ta có :
\(\left|x-2\right|\ge0\)
\(\Leftrightarrow\left|x-2\right|-1\ge-1\)
\(\Leftrightarrow B\ge-1\)
Dấu "=" xảy ra khi :
\(\left|x-2\right|=0\Leftrightarrow x=2\)
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c/ Với mọi x ta có :
\(\left|1-x\right|\ge0\)
\(\Leftrightarrow2\left|1-x\right|\ge0\)
\(\Leftrightarrow2\left|1-x\right|+1\ge1\)
\(\Leftrightarrow C\ge1\)
Dấu "=" xảy ra khi :
\(\left|1-x\right|=0\Leftrightarrow x=1\)
Vậy ...
