Question

Na PA a1=7 e r=3,calcule o vigésimo termo

Answer 1

vamos lá....

$a_n=a_{20}=? \\ a_1=7 \\ r=3 \\ n=20 \\ \\ Termo~~geral \\ \\ a_n=a_1+(n-1)r \\ \\ a_{20}=7+(20-1)(3) \\ \\ a_{20}=7+(19)(3) \\ \\ a_{20}=7+57 \\ \\ a_{20}=64$

Answer 2

a₂₀ = a₁ + 19.r
a₂₀ = 7 + 19.3
a₂₀ = 7 + 57
a₂₀ = 64