\(\begin{array}{l}
a)\,\,\,y = 3{x^2} - 1\\
D = R\\
\Rightarrow \forall x \in D \Rightarrow - x \in D\\
\Rightarrow f\left( { - x} \right) = 3{\left( { - x} \right)^2} - 1 = 3{x^2} - 1 = f\left( x \right)\\
\Rightarrow hs\,\,la\,\,ham\,\,chan.\\
b)\,\,\,y = {x^4} + 3x - 2\\
D = R\\
\Rightarrow \forall x \in D \Rightarrow - x \in D\\
\Rightarrow f\left( { - x} \right) = {\left( { - x} \right)^4} + 3\left( { - x} \right) - 2 = {x^4} - 3x - 2 \ne f\left( x \right)\\
\Rightarrow hs\,\,k\,\,la\,\,ham\,\,chan\,\,cung\,\,k\,\,la\,\,ham\,\,le.
\end{array}\)
