a) \(A=\left|x-1\right|+2018\)
Vì \(\left|x-1\right|\ge0\forall x\)
\(\Rightarrow A\ge2018\forall x\)
Dấu "=" xảy ra \(\Leftrightarrow x-1=0\Leftrightarrow x=1\)
\(Tacó:\)
\(|x-1|\ge0\Rightarrow|x-1|+2018\left(\cdot\right)\ge2018\)
\(\Rightarrow GTNNcua\left(\cdot\right)=2018\)
Dấu "=" xảy ra khi: x=1
Vậy (*) Đạt GTNN là: 2018 khi: x=1
b) \(B=\left(2x-1\right)^4-2015\)
Vì \(\left(2x-1\right)^4\ge0\forall x\)
\(\Rightarrow B\ge-2015\forall x\)
Dấu "=" xảy ra \(\Leftrightarrow2x-1=0\Leftrightarrow x=\frac{1}{2}\)
c) \(C=4-\left|3x+1\right|\)
Vì \(\left|3x+1\right|\ge0\forall x\)
\(\Rightarrow C\le4\forall x\)
Dấu "=" xảy ra \(\Leftrightarrow3x+1=0\Leftrightarrow x=\frac{-1}{3}\)