Question

a îmi trebuie repede​

Answer 1

Răspuns:

$\displaystyle\dfrac{1}{a_ka_{k+1}}=\dfrac{1}{r}\left(\dfrac{1}{a_k}-\dfrac{1}{a_{k+1}}\right)$

$b_n=\dfrac{1}{r}\left(\dfrac{1}{a_1}-\dfrac{1}{a_{n+1}}\right)\Rightarrow\displaystyle\lim_{n\to\infty}b_n=\dfrac{1}{ra_1}$

Explicație pas cu pas: