Question

quantos termos possui a P.A. (6.9.12.15...231)

Answer 1

a1=6
an=231
n=?
r=3
an=a1+(n-1)r
231=6+(n-1)3
231=6+3n
6+3n=231
3n+231-6
3n=225
n=225 ÷ 3
n=75