Respuesta :
a = 6
tn = a + (n - 1)d
t4 = 6 + 3d = 12
3d = 12 - 6 = 6
d = 6/3 = 2
f(n + 1) = f(n) + 2
tn = a + (n - 1)d
t4 = 6 + 3d = 12
3d = 12 - 6 = 6
d = 6/3 = 2
f(n + 1) = f(n) + 2