Question

Answer each question based on the following arithmetic sequence.

13, 10, 7, 4,.........
Part A
For the sequence listed above, what is
a
1
a
1
​
?


Part B
For the sequence listed above, what is
a
3
a
3
​
?

​Part C
​For the sequence listed above, what is its explicit equation?
​
(b)
A
an=−13+(n+1)(3)a_{n}=-13+(n+1)(3)a
n
​
=−13+(n+1)(3)
B
an=−3+(n−1)(13)a_{n}=-3+(n-1)(13)a
n
​
=−3+(n−1)(13)
C
an=3+(n−1)(−13)a_{n}=3+(n-1)(-13)a
n
​
=3+(n−1)(−13)
D
an=13+(n−1)(−3)a_{n}=13+(n-1)(-3)a
n
​
=13+(n−1)(−3)

Answer 1

Part A: a1 = 13

Part B: a3 = 7

Part C: common difference d = 10 − 13 = −3, so
a_n = 13 + (n−1)(−3) = 16 − 3n.

(Choice D: a_n = 13 + (n−1)(−3).)