Question

Write down in terms of n, an expression for the nth term of the following sequences:

a) 12 10 8 6 4
b) 25 20 15 10 5​

Answer 1

The formula for an arithmetic sequence is:

an = a1 + (n - 1)d

In which a1 is the first term and d is the common difference.

a) 12, 10, 8, 6, 4

an = 12 + (n - 1)-2

an = 12 -2n + 2

an = -2n + 14

b) 25, 20, 15, 10, 5

an = 25 + (n - 1)-5

an = 25 -5n + 5

an = -5n + 30