Question

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

Answer 1

a1 = 3

r = 8 - 3 = 5

a20 = ???

n = 20

a20 = 3 + (20 -1)5

a20 = 3 + 19 * 5

a20 = 98

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18/02/2016 
Sepauto - SSRC
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Answer 2

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

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

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

$a_{20}=3+95$

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