Tomamos como el límite
$$\lim_{x \to \frac{1}{2}^+}\left(\frac{\frac{1}{4} - x^{2}}{x + \frac{1}{2}}\right)$$
cambiamos
$$\lim_{x \to \frac{1}{2}^+}\left(\frac{\frac{1}{4} - x^{2}}{x + \frac{1}{2}}\right)$$
=
$$\lim_{x \to \frac{1}{2}^+}\left(\frac{\left(-1\right) \frac{1}{4} \left(2 x - 1\right) \left(2 x + 1\right)}{x + \frac{1}{2}}\right)$$
=
$$\lim_{x \to \frac{1}{2}^+}\left(\frac{1}{2} - x\right) = $$
$$\frac{1}{2} - \frac{1}{2} = $$
= 0
Entonces la respuesta definitiva es:
$$\lim_{x \to \frac{1}{2}^+}\left(\frac{\frac{1}{4} - x^{2}}{x + \frac{1}{2}}\right) = 0$$