Question

Determine o vigésimo quarto termo da P A (3,7,11,...).

Answer 1

$P.A(3,7,11,...)$

$a_{1}=3$
$a_{2}=7$

$r=a_{2}-a_{1}=7-3=4$

$a_{n}=a_{1}+(n-1)*r$
$a_{20}=a_{1}+(20-1)*r$
$a_{20}=a_{1}+19*r$
$a_{20}=3+19*4$
$a_{20}=3+76$

$\boxed{\boxed{a_{20}=79}}$