Докажите тождество: [latex] \frac{1}{\log_{a}k} + \frac{1}{\log_{a^2}k} + \frac{1}{\log_{a^3}k} + \frac{1}{\log_{a^4}k}+ \frac{1}{\log_{a^5}k} =15\log_{k}{a}[/latex]

[latex] \dfrac{1}{\log_{a}k} + \dfrac{1}{\log_{a^2}k} + \dfrac{1}{\log_{a^3}k} + \dfrac{1}{\log_{a^4}k}+ \dfrac{1}{\log_{a^5}k} =15\log_{k}{a} [/latex] Преобразовываем левую часть к правой: [latex] \dfrac{1}{\log_{a}k} + \dfrac{1}{\log_{a^2}k} + \dfrac{1}{\log_{a^3}k} + \dfrac{1}{\log_{a^4}k}+ \dfrac{1}{\log_{a^5}k} = \\\ = \dfrac{1}{\log_{a}k} + \dfrac{1}{ \frac{1}{2} \log_{a}k} + \dfrac{1}{ \frac{1}{3}\log_{a}k} + \dfrac{1}{ \frac{1}{4}\log_{a}k}+ \dfrac{1}{ \frac{1}{5}\log_{a}k} = \\\ = \dfrac{1}{\log_{a}k} + \dfrac{2}{ \log_{a}k} + \dfrac{3}{ \log_{a}k} + \dfrac{4}{ \log_{a}k}+ \dfrac{5}{ \log_{a}k} = \\\ = \dfrac{15}{ \log_{a}k}= \dfrac{15}{ \frac{1}{\log_{k}a} }=15\log_{k}a[/latex]