Question

determine o décimo segundo termo da P.A (- 8, - 3, 2...)​

Answer 1

Começamos determinando a razão:

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

Agora, utilizando a equação do termo geral, podemos calcular o 10° termo:

$a_n~=~a_1+(n-1).r\\\\\\a_{10}~=~-8+(10-1)\,.\,5\\\\\\a_{10}~=~-8+9\,.\,5\\\\\\a_{10}~=~-8+45\\\\\\\boxed{a_{10}~=~37}$