Tenemos la indeterminación de tipo
oo/oo,
tal que el límite para el numerador es
$$\lim_{x \to \infty}\left(\frac{\sqrt[3]{x} \left(3 x + 1\right)}{x + 1}\right) = \infty$$
y el límite para el denominador es
$$\lim_{x \to \infty} \sqrt[3]{2 x + 5} = \infty$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{x \to \infty}\left(\frac{x^{\frac{5}{6}} \left(3 x + 1\right)}{\sqrt[3]{2 x + 5} \left(x^{\frac{3}{2}} + \sqrt{x}\right)}\right)$$
=
Introducimos una pequeña modificación de la función bajo el signo del límite
$$\lim_{x \to \infty}\left(\frac{\sqrt[3]{x} \left(3 x + 1\right)}{\left(x + 1\right) \sqrt[3]{2 x + 5}}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{\frac{d}{d x} \frac{\sqrt[3]{x} \left(3 x + 1\right)}{x + 1}}{\frac{d}{d x} \sqrt[3]{2 x + 5}}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{3 \left(2 x + 5\right)^{\frac{2}{3}} \left(\frac{3 \sqrt[3]{x}}{x + 1} - \frac{\sqrt[3]{x} \left(3 x + 1\right)}{\left(x + 1\right)^{2}} + \frac{3 x + 1}{3 x^{\frac{2}{3}} \left(x + 1\right)}\right)}{2}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{\frac{d}{d x} \frac{3 \left(2 x + 5\right)^{\frac{2}{3}}}{2}}{\frac{d}{d x} \frac{1}{\frac{3 \sqrt[3]{x}}{x + 1} - \frac{\sqrt[3]{x} \left(3 x + 1\right)}{\left(x + 1\right)^{2}} + \frac{3 x + 1}{3 x^{\frac{2}{3}} \left(x + 1\right)}}}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{2 \left(\frac{9 x^{\frac{8}{3}}}{x^{4} + 4 x^{3} + 6 x^{2} + 4 x + 1} + \frac{6 x^{\frac{5}{3}}}{x^{4} + 4 x^{3} + 6 x^{2} + 4 x + 1} - \frac{18 x^{\frac{5}{3}}}{x^{3} + 3 x^{2} + 3 x + 1} + \frac{x^{\frac{2}{3}}}{x^{4} + 4 x^{3} + 6 x^{2} + 4 x + 1} - \frac{6 x^{\frac{2}{3}}}{x^{3} + 3 x^{2} + 3 x + 1} + \frac{15 x^{\frac{2}{3}}}{x^{2} + 2 x + 1} - \frac{18 x^{2}}{3 x^{\frac{10}{3}} + 9 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}} + 3 \sqrt[3]{x}} + \frac{9 x^{2}}{9 x^{\frac{10}{3}} + 18 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}}} - \frac{12 x}{3 x^{\frac{10}{3}} + 9 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}} + 3 \sqrt[3]{x}} + \frac{6 x}{9 x^{\frac{10}{3}} + 18 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}}} - \frac{2}{3 x^{\frac{10}{3}} + 9 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}} + 3 \sqrt[3]{x}} + \frac{1}{9 x^{\frac{10}{3}} + 18 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}}} + \frac{2}{x^{\frac{7}{3}} + 2 x^{\frac{4}{3}} + \sqrt[3]{x}}\right)}{\sqrt[3]{2 x + 5} \left(- \frac{6 x^{\frac{4}{3}}}{x^{3} + 3 x^{2} + 3 x + 1} - \frac{2 \sqrt[3]{x}}{x^{3} + 3 x^{2} + 3 x + 1} + \frac{6 \sqrt[3]{x}}{x^{2} + 2 x + 1} + \frac{6 x}{3 x^{\frac{8}{3}} + 6 x^{\frac{5}{3}} + 3 x^{\frac{2}{3}}} + \frac{6 x}{9 x^{\frac{8}{3}} + 9 x^{\frac{5}{3}}} + \frac{2}{3 x^{\frac{8}{3}} + 6 x^{\frac{5}{3}} + 3 x^{\frac{2}{3}}} + \frac{2}{9 x^{\frac{8}{3}} + 9 x^{\frac{5}{3}}} - \frac{2}{x^{\frac{5}{3}} + x^{\frac{2}{3}}}\right)}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{2 \left(\frac{9 x^{\frac{8}{3}}}{x^{4} + 4 x^{3} + 6 x^{2} + 4 x + 1} + \frac{6 x^{\frac{5}{3}}}{x^{4} + 4 x^{3} + 6 x^{2} + 4 x + 1} - \frac{18 x^{\frac{5}{3}}}{x^{3} + 3 x^{2} + 3 x + 1} + \frac{x^{\frac{2}{3}}}{x^{4} + 4 x^{3} + 6 x^{2} + 4 x + 1} - \frac{6 x^{\frac{2}{3}}}{x^{3} + 3 x^{2} + 3 x + 1} + \frac{15 x^{\frac{2}{3}}}{x^{2} + 2 x + 1} - \frac{18 x^{2}}{3 x^{\frac{10}{3}} + 9 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}} + 3 \sqrt[3]{x}} + \frac{9 x^{2}}{9 x^{\frac{10}{3}} + 18 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}}} - \frac{12 x}{3 x^{\frac{10}{3}} + 9 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}} + 3 \sqrt[3]{x}} + \frac{6 x}{9 x^{\frac{10}{3}} + 18 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}}} - \frac{2}{3 x^{\frac{10}{3}} + 9 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}} + 3 \sqrt[3]{x}} + \frac{1}{9 x^{\frac{10}{3}} + 18 x^{\frac{7}{3}} + 9 x^{\frac{4}{3}}} + \frac{2}{x^{\frac{7}{3}} + 2 x^{\frac{4}{3}} + \sqrt[3]{x}}\right)}{\sqrt[3]{2 x + 5} \left(- \frac{6 x^{\frac{4}{3}}}{x^{3} + 3 x^{2} + 3 x + 1} - \frac{2 \sqrt[3]{x}}{x^{3} + 3 x^{2} + 3 x + 1} + \frac{6 \sqrt[3]{x}}{x^{2} + 2 x + 1} + \frac{6 x}{3 x^{\frac{8}{3}} + 6 x^{\frac{5}{3}} + 3 x^{\frac{2}{3}}} + \frac{6 x}{9 x^{\frac{8}{3}} + 9 x^{\frac{5}{3}}} + \frac{2}{3 x^{\frac{8}{3}} + 6 x^{\frac{5}{3}} + 3 x^{\frac{2}{3}}} + \frac{2}{9 x^{\frac{8}{3}} + 9 x^{\frac{5}{3}}} - \frac{2}{x^{\frac{5}{3}} + x^{\frac{2}{3}}}\right)}\right)$$
=
$$\frac{3 \cdot 2^{\frac{2}{3}}}{2}$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 2 vez (veces)