Find the nth term and the indicated term of the arithmetic sequence whose initial term, a, and common difference, d, are
given.
-$$\begin{array} { l }
\mathrm { a } = 9 ; \mathrm { d } = - 9 \
\mathrm { a } _ { \mathrm { n } } = ? ; \mathrm { a } _ { 13 } = ?
\end{array}$$
A) $a _ { n } = 18 - 9 n ; a _ { 13 } = - 99$
B) $a _ { n } = 18 - 9 n ; a _ { 13 } = - 54$
C) $a _ { n } = 9 - 9 n ; a _ { 13 } = - 99$
D) $a _ { n } = 18 + 9 n ; a _ { 13 } = - 99$

Question

Find the nth term and the indicated term of the arithmetic sequence whose initial term, a, and common difference, d, are
given.
-$$\begin{array} { l } 
\mathrm { a } = 9 ; \mathrm { d } = - 9 \
\mathrm { a } _ { \mathrm { n } } = ? ; \mathrm { a } _ { 13 } = ?
\end{array}$$
A) $a _ { n } = 18 - 9 n ; a _ { 13 } = - 99$
B) $a _ { n } = 18 - 9 n ; a _ { 13 } = - 54$
C) $a _ { n } = 9 - 9 n ; a _ { 13 } = - 99$
D) $a _ { n } = 18 + 9 n ; a _ { 13 } = - 99$

Quizplus · Accepted Answer

The nth term of an arithmetic sequence is given by the formula:$a _ { n } = a + ( n - 1 ) d$where a is the initial term, d is the common difference, and n is the term number.In this case, the initial term is 9 and the common difference is -9. So, the nth term is:$a _ { n } = 9 + ( n - 1 ) ( - 9 ) = 9 - 9 n + 9 = 18 - 9 n$The 13th term is the term number 13, so we can substitute n = 13 into the formula for the nth term to get:$a _ { 13 } = 18 - 9 ( 13 ) = 18 - 117 = - 99$Therefore, the nth term is $a _ { n } = 18 - 9 n$ and the 13th term is $a _ { 13 } = - 99$.

Find the Nth Term and the Indicated Term of the Arithmetic