Respuesta :
Given:
The first four terms of a sequence are:
8, 5, 2, -1
To find:
The function that defines the given sequence.
Solution:
We have,
8, 5, 2, -1
The differences between two consecutive terms are:
[tex]5-8=-3[/tex]
[tex]2-5=-3[/tex]
[tex]-1-2=-3[/tex]
The given sequence has a common difference -3. It means the given sequence is an arithmetic sequence with first term 8 and common difference -3.
The nth terms of an arithmetic sequence is:
[tex]f(n)=a+(n-1)d[/tex], for [tex]n\geq 1[/tex]
Where, a is the first term and d is the common difference.
Putting [tex]a=8,d=-3[/tex], we get
[tex]f(n)=8+(n-1)(-3)[/tex]
[tex]f(n)=8-3(n-1)[/tex]
[tex]f(n)=-3(n-1)+8[/tex], for [tex]n\geq 1[/tex]
Therefore, the correct option is A.
