Question

qual o vigésimo termo da P.A.(3,8,...) ?

Answer 1

a20 = a1 + 19r                r= 8-3 = 5

a20 = 3 + 19 . 5

a20 = 3 + 95

a20 = 98

Answer 2

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

$a_{20}=3+(20-1)\cdot5$

$a_{20}=3+19\cdot5$

$a_{20}=3+95$

$\boxed{\boxed{ a_{20}=98}}$