Tomamos como el límite
$$\lim_{x \to 6^+}\left(\frac{- 5 x + \left(x^{2} - 6\right)}{14 x + \left(x^{2} + 48\right)}\right)$$
cambiamos
$$\lim_{x \to 6^+}\left(\frac{- 5 x + \left(x^{2} - 6\right)}{14 x + \left(x^{2} + 48\right)}\right)$$
=
$$\lim_{x \to 6^+}\left(\frac{\left(x - 6\right) \left(x + 1\right)}{\left(x + 6\right) \left(x + 8\right)}\right)$$
=
$$\lim_{x \to 6^+}\left(\frac{\left(x - 6\right) \left(x + 1\right)}{\left(x + 6\right) \left(x + 8\right)}\right) = $$
$$\frac{\left(-6 + 6\right) \left(1 + 6\right)}{\left(6 + 6\right) \left(6 + 8\right)} = $$
= 0
Entonces la respuesta definitiva es:
$$\lim_{x \to 6^+}\left(\frac{- 5 x + \left(x^{2} - 6\right)}{14 x + \left(x^{2} + 48\right)}\right) = 0$$