Question

Determine a formula geral da PA (-1,5)...

Answer 1

$a_n=a_1+r(n-1),\ n\geq1\ \ e\ \ n\in\mathbb{N}\\\\\\P.G.=(-1,\ 5,\ \cdots)\\\\a_1=-1\\\\r=a_2-a_1\longrightarrow{r}=5-(-1)\longrightarrow{r}=6\\\\\\a_n=-1+6(n-1)\\\\a_n=-1+6n-6\\\\\boxed{a_n=6n-7,\ n\geq1\ \ e\ \ n\in\mathbb{N}}$