The Common Difference
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| Key Lesson Marker |
Arithmetic Series
\[
\begin{align}
S_n &= \frac{n}{2}\left[ {2t_1 + \left( {n - 1} \right)d} \right] \\
S_n &= \frac{n}{2}\left( {t_1 + t_n } \right) \\
\end{align}
\]
\begin{align}
S_n &= \frac{n}{2}\left[ {2t_1 + \left( {n - 1} \right)d} \right] \\
S_n &= \frac{n}{2}\left( {t_1 + t_n } \right) \\
\end{align}
\]
\(n \) is the number of terms
\(S_n \) is the sum of \(n \) terms in the series
\(t_1 \) is the first term in the series
\(d \) is the common difference
\(t_n \) is the \(n^{th} \) term in the series