Question

encontre o vigésimo quinto termo da p.a.(3,8...)

Answer 1

$a_1 = 3 \\ r = 5 \\ a_{25} = ? \\ \\ a_n = a_1+(n-1).r \\ a_{25} = 3 + (25-1).5 \\ a_{25} = 3 + 24.5 \\ a_{25} = 3 + 120 \\ \\ a_{25} = 123$

Answer 2

an = a1 + ( n - 1 ). r
an = 3 + ( 25- 1 ). 5
an = 3 + 120
a25 = 123

tá valendo?
abraços!