\(\text{ C = 3 - | x + 2 |}\)
\(\left|x+2\right|\ge0\)
\(\Rightarrow3-\left|x+2\right|\ge3-0\)
\(\Rightarrow3-\left|x+2\right|\ge3\)
\(\Rightarrow C\ge3\)
\(\Rightarrow C=3\Leftrightarrow\left|x+2\right|=0\)
\(\Rightarrow x+2=0\)
\(\Rightarrow x=0-2\)
\(\Rightarrow x=-2\)
Vậy \(\text{Max C = 3 }\Leftrightarrow x=-2\)
\(!x+2!\ge0\Leftrightarrow3-!x+2!\le3\)
"=" xảy ra khi x=-2
\(!3x-15!\ge0\)
\(!3x-15!+8\ge8\)
dấu = xảy ra khi x=5
\(A=\left|3x-15\right|+8\)
\(\left|3x-15\right|\ge0\)
\(\Rightarrow\left|3x-15\right|+8\ge0+8\)
\(\Rightarrow\left|3x-15\right|+8\ge8\)
\(\Rightarrow A\ge8\)
\(\Rightarrow A=8\Leftrightarrow\left|3x-15\right|=0\)
\(\Rightarrow3x-15=0\)
\(\Rightarrow x=\left(0+15\right):3=5\)
Vậy \(MinA=8\Leftrightarrow x=5\)
A=|3x−15|+8
|3x−15|≥0
⇒|3x−15|+8≥0+8
⇒|3x−15|+8≥8
⇒A≥8
⇒A=8⇔|3x−15|=0
⇒3x−15=0
⇒x=(0+15):3=5
Vậy
