Question

encontre o termo geral da p.a.(12,16,20,...).

Answer 1

an =  a1 +  (n - 1).r

an = 12 + (n - 1).4

an = 12 + 4n - 4

an = 12 - 4 + 4n

an = 8 + 4n

an = 4n + 8

Answer 2

r = a2 - a1
r = 16 - 12
r = 4

an = a1 + (n - 1).r
an = 12 + (n - 1).4
an = 12 + 4n - 4
an = 12 - 4 + 4n
an = 8 + 4n
an = 4n + 8