Question

QUANTOS TERMOS TÊM A P.A FINITA (-6,-9,-12...,66)

Answer 1

an=66
a1=-6
n=?
r=-3

an=a1+(n-1).r
66=-6 + (n-1).(-3)
66-6=(n-1).(-3)
60=(n-1).(-3)
60:3=(n-1)
20=(n-1)
n=20-1
n=19