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Límite de la función ((7+4*n)/(8+3*n))^n/n^5

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Solución

Ha introducido [src]
     /         n\
     |/7 + 4*n\ |
     ||-------| |
     |\8 + 3*n/ |
 lim |----------|
n->oo|     5    |
     \    n     /
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n + 7}{3 n + 8}\right)^{n}}{n^{5}}\right)$$
Limit(((7 + 4*n)/(8 + 3*n))^n/n^5, n, oo, dir='-')
Método de l'Hopital
Tenemos la indeterminación de tipo
oo/oo,

tal que el límite para el numerador es
$$\lim_{n \to \infty} \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} = \infty$$
y el límite para el denominador es
$$\lim_{n \to \infty} n^{5} = \infty$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n + 7}{3 n + 8}\right)^{n}}{n^{5}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\frac{d}{d n} \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n}}{\frac{d}{d n} n^{5}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \left(\frac{n \left(- \frac{12 n}{\left(3 n + 8\right)^{2}} + \frac{4}{3 n + 8} - \frac{21}{\left(3 n + 8\right)^{2}}\right)}{\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}} + \log{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8} \right)}\right)}{5 n^{4}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \left(- \log{\left(3 \right)} + 2 \log{\left(2 \right)}\right)}{5 n^{4}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\frac{d}{d n} \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n}}{\frac{d}{d n} \frac{5 n^{4}}{- \log{\left(3 \right)} + 2 \log{\left(2 \right)}}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \left(\frac{n \left(- \frac{12 n}{\left(3 n + 8\right)^{2}} + \frac{4}{3 n + 8} - \frac{21}{\left(3 n + 8\right)^{2}}\right)}{\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}} + \log{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8} \right)}\right) \left(- \log{\left(3 \right)} + 2 \log{\left(2 \right)}\right)}{20 n^{3}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \left(- 4 \log{\left(2 \right)} \log{\left(3 \right)} + \log{\left(3 \right)}^{2} + 4 \log{\left(2 \right)}^{2}\right)}{20 n^{3}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\frac{d}{d n} \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n}}{\frac{d}{d n} \frac{20 n^{3}}{- 4 \log{\left(2 \right)} \log{\left(3 \right)} + \log{\left(3 \right)}^{2} + 4 \log{\left(2 \right)}^{2}}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \left(\frac{n \left(- \frac{12 n}{\left(3 n + 8\right)^{2}} + \frac{4}{3 n + 8} - \frac{21}{\left(3 n + 8\right)^{2}}\right)}{\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}} + \log{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8} \right)}\right) \left(- 4 \log{\left(2 \right)} \log{\left(3 \right)} + \log{\left(3 \right)}^{2} + 4 \log{\left(2 \right)}^{2}\right)}{60 n^{2}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \left(- 12 \log{\left(2 \right)}^{2} \log{\left(3 \right)} - \log{\left(3 \right)}^{3} + 8 \log{\left(2 \right)}^{3} + 6 \log{\left(2 \right)} \log{\left(3 \right)}^{2}\right)}{60 n^{2}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\frac{d}{d n} \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n}}{\frac{d}{d n} \frac{60 n^{2}}{- 12 \log{\left(2 \right)}^{2} \log{\left(3 \right)} - \log{\left(3 \right)}^{3} + 8 \log{\left(2 \right)}^{3} + 6 \log{\left(2 \right)} \log{\left(3 \right)}^{2}}}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \left(\frac{n \left(- \frac{12 n}{\left(3 n + 8\right)^{2}} + \frac{4}{3 n + 8} - \frac{21}{\left(3 n + 8\right)^{2}}\right)}{\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}} + \log{\left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8} \right)}\right) \left(- 12 \log{\left(2 \right)}^{2} \log{\left(3 \right)} - \log{\left(3 \right)}^{3} + 8 \log{\left(2 \right)}^{3} + 6 \log{\left(2 \right)} \log{\left(3 \right)}^{2}\right)}{120 n}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(- \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \log{\left(3 \right)} + 2 \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \log{\left(2 \right)}\right) \left(- 12 \log{\left(2 \right)}^{2} \log{\left(3 \right)} - \log{\left(3 \right)}^{3} + 8 \log{\left(2 \right)}^{3} + 6 \log{\left(2 \right)} \log{\left(3 \right)}^{2}\right)}{120 n}\right)$$
=
$$\lim_{n \to \infty}\left(\frac{\left(- \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \log{\left(3 \right)} + 2 \left(\frac{4 n}{3 n + 8} + \frac{7}{3 n + 8}\right)^{n} \log{\left(2 \right)}\right) \left(- 12 \log{\left(2 \right)}^{2} \log{\left(3 \right)} - \log{\left(3 \right)}^{3} + 8 \log{\left(2 \right)}^{3} + 6 \log{\left(2 \right)} \log{\left(3 \right)}^{2}\right)}{120 n}\right)$$
=
$$\infty$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 4 vez (veces)
Gráfica
Otros límites con n→0, -oo, +oo, 1
$$\lim_{n \to \infty}\left(\frac{\left(\frac{4 n + 7}{3 n + 8}\right)^{n}}{n^{5}}\right) = \infty$$
$$\lim_{n \to 0^-}\left(\frac{\left(\frac{4 n + 7}{3 n + 8}\right)^{n}}{n^{5}}\right) = -\infty$$
Más detalles con n→0 a la izquierda
$$\lim_{n \to 0^+}\left(\frac{\left(\frac{4 n + 7}{3 n + 8}\right)^{n}}{n^{5}}\right) = \infty$$
Más detalles con n→0 a la derecha
$$\lim_{n \to 1^-}\left(\frac{\left(\frac{4 n + 7}{3 n + 8}\right)^{n}}{n^{5}}\right) = 1$$
Más detalles con n→1 a la izquierda
$$\lim_{n \to 1^+}\left(\frac{\left(\frac{4 n + 7}{3 n + 8}\right)^{n}}{n^{5}}\right) = 1$$
Más detalles con n→1 a la derecha
$$\lim_{n \to -\infty}\left(\frac{\left(\frac{4 n + 7}{3 n + 8}\right)^{n}}{n^{5}}\right) = 0$$
Más detalles con n→-oo
Respuesta rápida [src]
oo
$$\infty$$