Question

determine o decimo segundo termo da PA (-8,-3,2)

Answer 1

Primeiramente, vamos encontrar a razão dessa PA

$r=a_2-a_1\\\\ r=-3-(-8)\\\\ r=-3+8\\\\ \boxed{\boxed{r=5}}$

Agora:

$a_n=a_1+(n-1)*r\\\\ a_1_2=a_1+11r\\\\ a_1_2=-8+11*5\\\\ a_1_2=-8+55\\\\ \boxed{\boxed{a_1_2=47}}$

Answer 2

a1=-8
n=12
a12=?
r=5
an=a1+(n-1).r
a12=-8+11.5
a12=-8+55
a12=47