Tenemos la indeterminación de tipo
0/0,
tal que el límite para el numerador es
$$\lim_{x \to 0^+}\left(\frac{\left(x^{3} - 6 x + 1\right) \sin^{2}{\left(5 x \right)}}{\left(x^{2} + 4\right) \tan{\left(12 x \right)}}\right) = 0$$
y el límite para el denominador es
$$\lim_{x \to 0^+} \operatorname{asin}{\left(x \left(x + 3\right) \right)} = 0$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{x \to 0^+}\left(\frac{\left(- 6 x + \left(x^{3} + 1\right)\right) \sin^{2}{\left(5 x \right)}}{\left(x^{2} + 4\right) \operatorname{asin}{\left(x^{2} + 3 x \right)} \tan{\left(12 x \right)}}\right)$$
=
Introducimos una pequeña modificación de la función bajo el signo del límite
$$\lim_{x \to 0^+}\left(\frac{\left(x^{3} - 6 x + 1\right) \sin^{2}{\left(5 x \right)}}{\left(x^{2} + 4\right) \tan{\left(12 x \right)} \operatorname{asin}{\left(x \left(x + 3\right) \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \frac{\left(x^{3} - 6 x + 1\right) \sin^{2}{\left(5 x \right)}}{\left(x^{2} + 4\right) \tan{\left(12 x \right)}}}{\frac{d}{d x} \operatorname{asin}{\left(x \left(x + 3\right) \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\sqrt{- x^{2} \left(x + 3\right)^{2} + 1} \left(- \frac{2 x \left(x^{3} - 6 x + 1\right) \sin^{2}{\left(5 x \right)}}{\left(x^{2} + 4\right)^{2} \tan{\left(12 x \right)}} + \frac{\left(3 x^{2} - 6\right) \sin^{2}{\left(5 x \right)}}{\left(x^{2} + 4\right) \tan{\left(12 x \right)}} + \frac{\left(- 12 \tan^{2}{\left(12 x \right)} - 12\right) \left(x^{3} - 6 x + 1\right) \sin^{2}{\left(5 x \right)}}{\left(x^{2} + 4\right) \tan^{2}{\left(12 x \right)}} + \frac{10 \left(x^{3} - 6 x + 1\right) \sin{\left(5 x \right)} \cos{\left(5 x \right)}}{\left(x^{2} + 4\right) \tan{\left(12 x \right)}}\right)}{2 x + 3}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{2 x^{4} \sin^{2}{\left(5 x \right)}}{3 x^{4} \tan{\left(12 x \right)} + 24 x^{2} \tan{\left(12 x \right)} + 48 \tan{\left(12 x \right)}} - \frac{12 x^{3} \sin^{2}{\left(5 x \right)} \tan^{2}{\left(12 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} - \frac{12 x^{3} \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} + \frac{10 x^{3} \sin{\left(5 x \right)} \cos{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}} + \frac{12 x^{2} \sin^{2}{\left(5 x \right)}}{3 x^{4} \tan{\left(12 x \right)} + 24 x^{2} \tan{\left(12 x \right)} + 48 \tan{\left(12 x \right)}} + \frac{3 x^{2} \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}} - \frac{2 x \sin^{2}{\left(5 x \right)}}{3 x^{4} \tan{\left(12 x \right)} + 24 x^{2} \tan{\left(12 x \right)} + 48 \tan{\left(12 x \right)}} + \frac{72 x \sin^{2}{\left(5 x \right)} \tan^{2}{\left(12 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} + \frac{72 x \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} - \frac{60 x \sin{\left(5 x \right)} \cos{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}} - \frac{12 \sin^{2}{\left(5 x \right)} \tan^{2}{\left(12 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} - \frac{12 \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} - \frac{6 \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}} + \frac{10 \sin{\left(5 x \right)} \cos{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{2 x^{4} \sin^{2}{\left(5 x \right)}}{3 x^{4} \tan{\left(12 x \right)} + 24 x^{2} \tan{\left(12 x \right)} + 48 \tan{\left(12 x \right)}} - \frac{12 x^{3} \sin^{2}{\left(5 x \right)} \tan^{2}{\left(12 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} - \frac{12 x^{3} \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} + \frac{10 x^{3} \sin{\left(5 x \right)} \cos{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}} + \frac{12 x^{2} \sin^{2}{\left(5 x \right)}}{3 x^{4} \tan{\left(12 x \right)} + 24 x^{2} \tan{\left(12 x \right)} + 48 \tan{\left(12 x \right)}} + \frac{3 x^{2} \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}} - \frac{2 x \sin^{2}{\left(5 x \right)}}{3 x^{4} \tan{\left(12 x \right)} + 24 x^{2} \tan{\left(12 x \right)} + 48 \tan{\left(12 x \right)}} + \frac{72 x \sin^{2}{\left(5 x \right)} \tan^{2}{\left(12 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} + \frac{72 x \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} - \frac{60 x \sin{\left(5 x \right)} \cos{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}} - \frac{12 \sin^{2}{\left(5 x \right)} \tan^{2}{\left(12 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} - \frac{12 \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan^{2}{\left(12 x \right)} + 12 \tan^{2}{\left(12 x \right)}} - \frac{6 \sin^{2}{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}} + \frac{10 \sin{\left(5 x \right)} \cos{\left(5 x \right)}}{3 x^{2} \tan{\left(12 x \right)} + 12 \tan{\left(12 x \right)}}\right)$$
=
$$\frac{25}{144}$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 1 vez (veces)