Lời giải

\( f'(x) f(x) = x^4 + x^2 \)

\( \Rightarrow \int f'(x) f(x) \, dx = \frac{x^5}{5} + \frac{x^3}{3} + C \)

\( \Rightarrow \frac{(f(x))^2}{2} = \frac{x^5}{5} + \frac{x^3}{3} + C \)

\( f(0) = 2  \Rightarrow C = 2. \)

 \( \Rightarrow (f(x))^2 = \frac{2x^5}{5} + \frac{2x^3}{3} + 4 \)

 \( (f(2))^2 = \frac{332}{15} \quad \Rightarrow \boxed{A} \)