a) \(y=f\left(x\right)=\sqrt{x^2}\)
\(\Rightarrow y=f\left(1\right)=\sqrt{1^2}=1\)
\(\Rightarrow y=f\left(-2\right)=\sqrt{\left(-2\right)^2}=2\)
b) \(f\left(x\right)=\sqrt{x^2}=2\)
\(\Leftrightarrow f\left(x\right)=x=2\)
Vậy x=2 để \(f\left(x\right)=2\)