Question

Qual o Vigésimo termo da P. A (-8,-3,2,7,...)?

Answer 1

a(20) = ?
a(1) = - 8
r = 5
n = 20

a(n) = a(1) + (n - 1)r
a(20) = - 8 + (20 - 1)5
a(20) = - 8 + 19*5 = - 8 + 95
a(20) = 87

O vigésimo termo é 87

Answer 2

$\begin{array}{l}\sf a_n=a_1+(n-1)\cdot r\\\\\sf a_{20}=-8+(20-1)\cdot5\\\\\sf a_{20}=-8+19\cdot5\\\\\sf a_{20}=-8+95\\\\\boxed{\boxed{\sf a_{20}= 87}} \end{array}$