Tomamos como el límite
$$\lim_{x \to 0^+}\left(\frac{3 x^{2} + 9}{\left(x^{2} + x\right)^{2}}\right)$$
cambiamos
$$\lim_{x \to 0^+}\left(\frac{3 x^{2} + 9}{\left(x^{2} + x\right)^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{3 x^{2} + 9}{x^{2} \left(x + 1\right)^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{3 \left(x^{2} + 3\right)}{x^{2} \left(x + 1\right)^{2}}\right) = $$
False
= oo
Entonces la respuesta definitiva es:
$$\lim_{x \to 0^+}\left(\frac{3 x^{2} + 9}{\left(x^{2} + x\right)^{2}}\right) = \infty$$