If the sum of the first 20 terms of the series $\log_{(7^{1/2})}x + \log_{(7^{1/3})}x + \log_{(7^{1/4})}x + \ldots$ is 460, then $x$ is equal to: (1) $7^2$ (2) $7^{1/2}$ (3) $e^2$ (4) $7^{46/21}$
If the sum of the first 20 terms of the series $\log_{(7^{1/2})}x + \log_{(7^{1/3})}x + \log_{(7^{1/4})}x + \ldots$ is 460, then $x$ is equal to:\\
(1) $7^2$\\
(2) $7^{1/2}$\\
(3) $e^2$\\
(4) $7^{46/21}$