Question

PA= a1=1 si a5=5 calculati a2018

Answer 1

Mai intai calculam ratia:

$a_5=a_1+4r\\5=1+4r\\4r=4\\\boxed{r=1}\\a_{2018}=a_1+2017r=1+2017=2018$

Answer 2

a1=1 ; a5=13 ; calculam ratia = r ; a5 = a1+4r ; 13 = 1+4r ; 4r = 12, r = 12/4 = 3

a2018 = a1+2017*r = 1+2017*3 = 1+6051 = 6052