$$$11^{- k} 4^{k}$$$の積分

$$$\int 11^{- k} 4^{k}\, dk$$$ を求めよ。

入力は次のように書き換えられます: $$$\int{11^{- k} 4^{k} d k}=\int{\left(\frac{4}{11}\right)^{k} d k}$$$。

Apply the exponential rule $$$\int{a^{k} d k} = \frac{a^{k}}{\ln{\left(a \right)}}$$$ with $$$a=\frac{4}{11}$$$:

$${\color{red}{\int{\left(\frac{4}{11}\right)^{k} d k}}} = {\color{red}{\frac{\left(\frac{4}{11}\right)^{k}}{\ln{\left(\frac{4}{11} \right)}}}}$$

したがって、

$$\int{\left(\frac{4}{11}\right)^{k} d k} = \frac{\left(\frac{4}{11}\right)^{k}}{\ln{\left(\frac{4}{11} \right)}}$$

簡単化せよ:

$$\int{\left(\frac{4}{11}\right)^{k} d k} = \frac{\left(\frac{4}{11}\right)^{k}}{- \ln{\left(11 \right)} + 2 \ln{\left(2 \right)}}$$

積分定数を加える:

$$\int{\left(\frac{4}{11}\right)^{k} d k} = \frac{\left(\frac{4}{11}\right)^{k}}{- \ln{\left(11 \right)} + 2 \ln{\left(2 \right)}}+C$$

$$$\int 11^{- k} 4^{k}\, dk = \frac{\left(\frac{4}{11}\right)^{k}}{- \ln\left(11\right) + 2 \ln\left(2\right)} + C$$$A