Question

quantos termis possui a pa (6,9,12,15,...231

Answer 1

an = a1 + ( n-1) .r
231 = 6 + (n-1) .3
231 = 6 + 3n-3
231 = 3n + 3
231 -3 = 3n
3n = 228
n = 228/3
n = 76 termos    ok