Question

calculati : S2 va rog

Answer 1

Folosim relația:

$\it \dfrac{2}{k(k+2)} = \dfrac{1}{k} - \dfrac{1}{k+2}$

$\it S_2 = \dfrac{1}{1} -\dfrac{1}{3} +\dfrac{1}{3} -\dfrac{1}{5}+\dfrac{1}{5} -\dfrac{1}{7}+ ... +\dfrac{1}{13} -\dfrac{1}{15} = 1 -\dfrac{1}{15}$