Question

Calcule o quadragésimo segundo termo da PA (4,8,12,16, ...)

Answer 1

Achando a razão da PA

r = 8 - 4

r = 4

a42 = a1 + 41r

a42 = 4 + 41*4

a42 = 4 + 164

a42 = 168

atte Colossoblack

Answer 2

$\large\displaystyle\begin{gathered}\sf a_n=a_1+(n-1)\cdot\underbrace{\sf (a_2-a_1)}_{\sf r}\end{gathered}$

$\large\displaystyle\begin{gathered}\sf a_{42}=4+(42-1)\cdot(8-4)\end{gathered}$

$\large\displaystyle\begin{gathered}\sf a_{42}=4+41\cdot4\end{gathered}$

$\large\displaystyle\begin{gathered}\sf a_{42}=4+164\end{gathered}$

$\large\displaystyle\text{ \begin{gathered}\boxed{\boxed{\sf a_{42}=168}}\end{gathered} }$