Tomamos como el límite
$$\lim_{x \to 0^+}\left(\frac{3 x \sin^{2}{\left(4 \right)}}{- x^{4} + x^{2}}\right)$$
cambiamos
$$\lim_{x \to 0^+}\left(\frac{3 x \sin^{2}{\left(4 \right)}}{- x^{4} + x^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{3 x \sin^{2}{\left(4 \right)}}{\left(-1\right) x^{2} \left(x - 1\right) \left(x + 1\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{3 \sin^{2}{\left(4 \right)}}{x^{3} - x}\right) = $$
False
= oo
Entonces la respuesta definitiva es:
$$\lim_{x \to 0^+}\left(\frac{3 x \sin^{2}{\left(4 \right)}}{- x^{4} + x^{2}}\right) = \infty$$