Question

determine o vigésimo termo da p.a (2,12,22,...)

Answer 1

αn = α1 + (n - 1).r
a20 = 2 + (20 - 1).10
a20 = 2 + 19.10
a20 = 192

Answer 2

$a_n=a_1+(n-1)\cdot r$

$a_{20}=2+(20-1)\cdot10$

$a_{20}=2+19\cdot10$

$a_{20}=2+190$

$\red{\boldsymbol{a_{20}=192 }}$