Question

1. Write an equation for the nth term of the Arithmetic sequence. Use the

Formula: an = a + (n - 1)d
2. Identify if the given sequence is Arithmetic, Geometric, or neither.
20, 15, 10, 5

Answer 1

Explanation:

Remark: This is an arithmetic sequence. Rather than going up, it is going down. Still it is an arithmetic sequence.

Givens

a1 = 20

d = -5

Formula

tn = a1 + (n-1)*-5 Remove the brackets

tn = 20 - 5n + 5

tn = 25 - 5n

So just to confirm it works, let n = 4 (which makes t4 = 5 as is given).

t4 = 25 - 5*4

t4 = 25 - 20

t4 = 5 which is exactly what t4 is