Question

Вычислите:
а) 125 + 25 + 5 + 1 + ...
б) -6 + 2/3 - 2/27 + 2/243 - ...

Answer 1

$sum_{n=1}^{infty} frac{n}{5} = frac{125}{1- frac{1}{5}} = frac{125}{0,8}=156,25 \ sum_{n=1}^{infty} -frac{n}{9} = frac{-6}{1- (-frac{1}{9}) } = frac{-6}{ frac{10}{9}}=-5,4$