Tomamos como el límite
$$\lim_{x \to 0^+}\left(\frac{x^{4} + 3 x^{2}}{x^{4} + 2 x^{2}}\right)$$
cambiamos
$$\lim_{x \to 0^+}\left(\frac{x^{4} + 3 x^{2}}{x^{4} + 2 x^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{x^{2} \left(x^{2} + 3\right)}{x^{2} \left(x^{2} + 2\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{x^{2} + 3}{x^{2} + 2}\right) = $$
$$\frac{0^{2} + 3}{0^{2} + 2} = $$
= 3/2
Entonces la respuesta definitiva es:
$$\lim_{x \to 0^+}\left(\frac{x^{4} + 3 x^{2}}{x^{4} + 2 x^{2}}\right) = \frac{3}{2}$$