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wcaprarBest ResponseYou've already chosen the best response.1
\[\sum_{n=2}^{\infty} 2^n/3*5^{n+2}\]
 one year ago

wcaprarBest ResponseYou've already chosen the best response.1
I see that you can take out the 5^2 and multiply that with three then simplify to get \[(1/75)*(2/5)^n\] which is a geometric series. But when I solve it out like you would a regular geometric series I get 1/45. But wolframalpha says 20
 one year ago

joemath314159Best ResponseYou've already chosen the best response.1
your idea is correct. lets make sure the arithmetic is correct
 one year ago

joemath314159Best ResponseYou've already chosen the best response.1
\[\frac{1}{75}\sum_{n=2}^{\infty}\left(\frac{2}{5}\right)^n=\frac{1}{75}\left(\frac{\frac{4}{625}}{1\frac{2}{5}}\right)\]
 one year ago

wcaprarBest ResponseYou've already chosen the best response.1
How do you get 4/625 on top?
 one year ago

joemath314159Best ResponseYou've already chosen the best response.1
we are starting at n=2, not n=1. The first term of the sequence is 4/625.
 one year ago
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