Question

Find a pattern for a sequence 17, 13, 9, 5,

Answer 1

it minus’ 4 every time

Answer 2

Answer: an=21-4n

Explanation:

17, 13, 9, 5, ...

13-17=-4

9-13=-4

5-9=-4

This sequence is an arithmetic progression a₁=17 d=-4

Hence,

`a_n= a_1+(n-1)d\\\\a_n=17+(n-1)(-4)\\\\a_n=17-4n+4\\\\a_n=21-4n,\ \ \ \ n=1, 2, 3, 4, ...`