Respostas

2013-06-25T19:04:25-03:00

-16,-18,-20,-22,-24,-26,-28,-30,-32,-34,-36,-38......

A12=-16+(12-1)-2

A12=-16+(11)-2

A12=-16-22

A12=-38

1 3 1
  • Usuário do Brainly
2013-06-26T03:26:21-03:00

Observe que:

 

\text{a}_{\text{n}}=\text{a}_1+(\text{n}-1)\cdot\text{r}

 

Segundo o enunciado, \text{a}=-16 e \text{r}=-2.

 

Desta maneira:

 

-38=-16+(\text{n}-1)\cdot(-2)

 

Donde, segue:

 

-38=-16-2\text{n}+2

 

2\text{n}=38-14

 

2\text{n}=24

 

Dividindo ambos os membros por 2, obtemos:

 

\text{n}=12

 

Logo, -38 é o 12^{\circ} termo desta P.A.