[tex]\it 5)\ \dfrac{a_{k-1}+a_k}{a_k+a_{k+1}} = \dfrac{a_{k-1}+a_k }{a_{k-1}\cdot q+a_k\cdot q} = \dfrac{a_{k-1}+a_k }{(a_{k-1}+a_k)\cdot q} = \dfrac{1}{q}[/tex]
Suma din enunț devine :
1/q +1/q +1/q + ... + 1/q (2013 termeni)
S= 2013 · (1/q) =2013·(1/2013) =1
