Antwort
$S_n = \frac{a_1(1 - r^n)}{1 - r}$.
Erklärung
Multiplying $S_n$ by $r$ and subtracting $r S_n$ from $S_n$ cancels intermediate terms, yielding $S_n(1 - r) = a_1(1 - r^n)$.
Start / Bibliothek / Gaokao essentials: original practice / Synthetische Lernkarte
What is the formula for the sum of the first $n$ terms of a geometric sequence with first term $a_1$ and common ratio $r \neq 1$?
Lernkarte aus dem Deck Gaokao essentials: original practice.