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Flashcards
2021-09-18
What’s the format of a general arithmetic sequence term $U_n$ for common difference $d$ and start term $a$??
$$ U_n = (n - 1)d + a $$
What’s the formula for the sum $S_n$ up to term $n$ of a sequence with start $a$ and common difference $d$??
$$ S_n = \frac{n}{2}\left( (n - 1)d + 2a \right) $$
What’s the formula for the sum $S_n$ of an arithmetic sequence between terms $a$ and $l$??
$$ S_n = \frac{n}{2}\left( a + l \right) $$
What does it mean for a geometric sequence to be divergent??
The terms get further and further apart.
What does it mean for a geometric sequence to be convergent??
The terms get closer and closer together.
What must be true about $r$ for a convergent geometric series??
$$ |r| < 1 $$
What must be true about $r$ for a divergent geometric series??
$$ |r| > 1 $$
2021-10-03
What is the formula for the sum of a convergent geometric sequence with $|r| < 1$??
$$ \frac{a}{1 - r} $$
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date: 2021-09-18 12:08
tags:
- '@?maths'
- '@?school'
- '@?public'
title: Maths - Series