Question

Calculati ; exercitiul se afla in imagine

Answer 1

Răspuns:2014/2015........

Answer 2

$S_4 = \dfrac{2}{1 \cdot 3} + \dfrac{2}{3 \cdot 5} + .... + \dfrac{2}{2013 \cdot 2015} \Rightarrow S_4= ( 1 - \dfrac{1}{3} ) + ( \dfrac{1}{3} - \dfrac{1}{5} ) + ... + ( \dfrac{1}{2013} - \dfrac{1}{2015}) \Rightarrow S_4 = 1 - \dfrac{1}{2015} \Rightarrow S_4= \dfrac{2015}{2015} - \dfrac{1}{2015} \Rightarrow \boxed{S_4= \dfrac{2014}{2015}}$