Question

calcule o decimo oitavo termo da p.a(4,9,14....)

Answer 1

$P.A(4,9,14,...)\\\\a_1=4\\a_2=9\\r=a_2-a_1\\r=9-4\\r=5\\n=18\\a_n=a_{18}=?\\\\a_n=a_1+(n-1)\cdot{r}\\a_{18}=4+(18-1)\cdot5\\a_{18}=4+17\cdot5\\a_{18}=4+85\\a_{18}=89$

Answer 2

a18=4+(18-1).5

a18=4+17.5

a18=4+85

a18=89