Question

Vă rog !!! Dau coroana !!!​

Answer 1

Răspuns:

Explicație pas cu pas:

Answer 2

a)

$\it S_n=\dfrac{1}{3}\cdot\dfrac{\dfrac{1}{3^{n-1}}-1}{\dfrac{1}{3}-1}=\dfrac{1}{3}\cdot\dfrac{\dfrac{3^{n-1}-1}{3^{n-1}}}{\dfrac{2}{3}}= \dfrac{1}{2}\cdot\dfrac{3^{n-1}-1}{3^{n-1}}=\dfrac{1}{2}-\dfrac{1}{2\cdot3^{n-1}}$

b)

$\it S_n=\dfrac{1}{3}+\dfrac{3^{n-1}-1}{3-1}=\dfrac{1}{3}+\dfrac{3^{n-1}-1}{2}=\dfrac{3^{n}-1}{6}$