Tomamos como el límite
$$\lim_{x \to a^+}\left(\frac{x^{2} + \left(x - 2\right)}{- a^{2} + x^{2}}\right)$$
cambiamos
$$\lim_{x \to a^+}\left(\frac{x^{2} + \left(x - 2\right)}{- a^{2} + x^{2}}\right)$$
=
$$\lim_{x \to a^+}\left(\frac{\left(x - 1\right) \left(x + 2\right)}{\left(- a + x\right) \left(a + x\right)}\right)$$
=
$$\lim_{x \to a^+}\left(\frac{x^{2} + x - 2}{- a^{2} + x^{2}}\right) = $$
$$\frac{a^{2} + a - 2}{- a^{2} + a^{2}} = $$
= oo*sign((-2 + a + a^2)/a)
Entonces la respuesta definitiva es:
$$\lim_{x \to a^+}\left(\frac{x^{2} + \left(x - 2\right)}{- a^{2} + x^{2}}\right) = \infty \operatorname{sign}{\left(\frac{a^{2} + a - 2}{a} \right)}$$