Question

qual e o 20° termo da PA (3,8,..)?

Answer 1

$a_{n} = a_{1} (n-1)*r$
r=5
$a_{1} =3$
n = 20

$a_{20} = 3+(20-1)*5$
$a_{20} = 3 + 95$
$a_{20} = 98$

Answer 2

$PA (3,8,..)\\\\\\ a_{1} =3\\ a_{n} =a_{20} =?\\ n=20\\ r=5\\\\\\ a_{n} = a_{1} +(n-1)*r\\\\\\ a_{20} =3 +(20-1)*5\to \\\\ a_{20} =3 +19*5\to\\\\ a_{20} =3 +95\to\\\\ a_{20} =98$