Deret Aritmetika

Deret aritmetika: \(2 + 14 + 26 + \: \dotso\)

Suku awal: \(a = 2\)

Beda: \(b = 14 − 2 = 12\)

(A)   Suku ke 13

\begin{equation*}
\begin{split}
U_n & = a + (n - 1)b \\\\
U_{13} & = 2 + (13 - 1) \: 12 \\\\
U_{13} & = 146
\end{split}
\end{equation*}

(B)   Jumlah suku-suku sampai dengan suku ke 13

\begin{equation*}
\begin{split}
S_n & = \frac{n}{2} [a + U_n] \\\\
S_{13} & = \frac{13}{2} [2 + 146] \\\\
S_{13} & = \frac{13}{2} [148] \\\\
S_{13} & = 962
\end{split}
\end{equation*}

(C)   Suku tengah