Respuesta :
Answer:
The general rule is [tex]a_n = -2 - 5(n-1)[/tex]
Step-by-step explanation:
Arithmetic sequence:
In an arithmetic sequence, the difference between consecutive terms is always the same, and this difference is called common difference.
The general rule of an arithmetic sequence is given by:
[tex]a_{n} = a_1 + (n-1)d[/tex]
In which [tex]a_1[/tex] is the first term and d is the common difference.
We can also find the nth term as a function of a term m, using:
[tex]a_n = a_m + (n-m)d[/tex]
a3 = -12 and a8 = -37
First we find the common difference. So
[tex]a_n = a_m + (n-m)d[/tex]
[tex]a_8 = a_3 + (8-3)d[/tex]
[tex]-37 = -12 + 5d[/tex]
[tex]5d = -25[/tex]
[tex]d = -\frac{25}{5}[/tex]
[tex]d = -5[/tex]
So
[tex]a_n = a_1 - 5(n-1)[/tex]
Finding the first term:
[tex]a_n = a_1 - 5(n-1)[/tex]
Since [tex]a_3 = -12[/tex]
[tex]a_n = a_1 - 5(n-1)[/tex]
[tex]a_3 = a_1 - 5(3-1)[/tex]
[tex]a_1 = a_3 + 10 = -12 + 10 = -2[/tex]
So the general rule is:
[tex]a_n = a_1 - 5(n-1)[/tex]
[tex]a_n = -2 - 5(n-1)[/tex]
