a) Ta có: \(\left|x+2\right|\ge0\left(\forall x\right)\)
\(\Rightarrow15-\left|x+2\right|\le15\left(\forall x\right)\)
Dấu "=" xảy ra khi \(x+2=0\Rightarrow x=-2\)
Vậy Amax = 15 khi x = -2
b) Ta có: \(\left|y-4\right|\ge0\left(\forall x\right)\)
\(\Rightarrow\left|y-4\right|+20\ge20\left(\forall x\right)\)
Dấu" =" xảy ra khi \(y-4=0\Rightarrow y=4\)
Vậy Bmin = 20 khi y = 4
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+) \(A=15-\left|x+2\right|\le15\)
Dấu bằng xảy ra
\(\Leftrightarrow x+2=0\Leftrightarrow x=-2\)
+) \(B=\left|y-4\right|+20\ge20\)
Dấu bằng xảy ra
\(\Leftrightarrow y-4=0\Leftrightarrow x=4\)
