Question

Determine o 100º termo da P.A(-20, -18, -16,...)



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Answer 1

$\mathrm{Progress\tilde{a}o\ aritm\acute{e}tica}\Longrightarrow \{a_1,a_2,a_3,\dots\}\Longrightarrow\{-20,-18,-16,\dots\}$

$\boxed{a_n=a_k+(n-k)r}\Longleftarrow \mathrm{Termo\ geral\ de\ uma\ PA.}$

$a_2=a_1+r\Longrightarrow r=a_2-a_1=-18-(-20)\ \therefore\ \boxed{r=2}$

$a_{100}=a_1+99r\Longrightarrow a_{100}=-20+99(2)\ \therefore\ \boxed{a_{100}=178}$