Tomamos como el límite
$$\lim_{x \to k^+}\left(\frac{9 x^{2} + \left(3 - 4 x\right)}{x^{2} - 9}\right)$$
cambiamos
$$\lim_{x \to k^+}\left(\frac{9 x^{2} + \left(3 - 4 x\right)}{x^{2} - 9}\right)$$
=
$$\lim_{x \to k^+}\left(\frac{9 x^{2} - 4 x + 3}{\left(x - 3\right) \left(x + 3\right)}\right)$$
=
$$\lim_{x \to k^+}\left(\frac{9 x^{2} - 4 x + 3}{x^{2} - 9}\right) = $$
$$\frac{9 k^{2} - 4 k + 3}{k^{2} - 9} = $$
= (3 - 4*k + 9*k^2)/(-9 + k^2)
Entonces la respuesta definitiva es:
$$\lim_{x \to k^+}\left(\frac{9 x^{2} + \left(3 - 4 x\right)}{x^{2} - 9}\right) = \frac{9 k^{2} - 4 k + 3}{k^{2} - 9}$$