Tomamos como el límite
$$\lim_{x \to 10^+}\left(\frac{- 10 x + \left(x^{2} + 9\right)}{x^{2} - 81}\right)$$
cambiamos
$$\lim_{x \to 10^+}\left(\frac{- 10 x + \left(x^{2} + 9\right)}{x^{2} - 81}\right)$$
=
$$\lim_{x \to 10^+}\left(\frac{\left(x - 9\right) \left(x - 1\right)}{\left(x - 9\right) \left(x + 9\right)}\right)$$
=
$$\lim_{x \to 10^+}\left(\frac{x - 1}{x + 9}\right) = $$
$$\frac{-1 + 10}{9 + 10} = $$
= 9/19
Entonces la respuesta definitiva es:
$$\lim_{x \to 10^+}\left(\frac{- 10 x + \left(x^{2} + 9\right)}{x^{2} - 81}\right) = \frac{9}{19}$$