Question

Necesito resolver esta sumatoria urgente

Answer 1

$\displaystyle\sum_{i=1}^{10}\dfrac{9}{10^i}=9\sum_{i=1}^{10}\dfrac{1}{10^i}=9\times\dfrac{1/10-(1/10)^{10+1}}{1-1/10}\\\\\\\boxed{\sum_{i=1}^{10}\dfrac{9}{10^i}=1-\dfrac{1}{10^{10}}}$