Write a formula for the general term (the nth term) of the arithmetic sequence. Then use the formula for an to find a20,
the 20th term of the sequence.
-$$a _ { 1 } = - 7 , d = 0.5$$
A) $a _ { n } = - 7 n + 7.5 ; a _ { 20 } = - 132.5$
B) $a _ { n } = - 7 n + 0.5 ; a _ { 20 } = - 139.5$
C) $a _ { n } = 0.5 n - 7 ; a _ { 20 } = 3$
D) $a _ { n } = 0.5 n - 7.5 ; a _ { 20 } = 2.5$

Question

Quizplus · Accepted Answer

The formula for the nth term of an arithmetic sequence is $a_n = a_1 + (n - 1)d$, where $a_1$ is the first term and $d$ is the common difference. Substituting $a_1 = -7$ and $d = 0.5$ gives $a_n = -7 + (n - 1)(0.5) = -7 + 0.5n - 0.5 = 0.5n - 7.5$. For $n = 20$, $a_{20} = 0.5(20) - 7.5 = 10 - 7.5 = 2.5$.

Write a Formula for the General Term (The Nth Term) a1=−7,d=0.5a _ { 1 } = - 7 , d = 0.5a1​=−7,d=0.5

Write a Formula for the General Term (The Nth Term) $a _ { 1 } = - 7 , d = 0.5$