Tomamos como el límite
$$\lim_{x \to 3^+}\left(\frac{- 5 x + \left(x^{2} + 6\right)}{3 x^{2} - 9}\right)$$
cambiamos
$$\lim_{x \to 3^+}\left(\frac{- 5 x + \left(x^{2} + 6\right)}{3 x^{2} - 9}\right)$$
=
$$\lim_{x \to 3^+}\left(\frac{\left(x - 3\right) \left(x - 2\right)}{3 x^{2} - 9}\right)$$
=
$$\lim_{x \to 3^+}\left(\frac{\left(x - 3\right) \left(x - 2\right)}{3 \left(x^{2} - 3\right)}\right) = $$
$$\frac{\left(-3 + 3\right) \left(-2 + 3\right)}{3 \left(-3 + 3^{2}\right)} = $$
= 0
Entonces la respuesta definitiva es:
$$\lim_{x \to 3^+}\left(\frac{- 5 x + \left(x^{2} + 6\right)}{3 x^{2} - 9}\right) = 0$$