-17; -14; -11...Найдите а81

Question

-17; -14; -11...
Найдите а81

Answer 1

A1=-17; d=3
a81=a1+(n-1)*d
a81=-17+(81-1)*3=240-17=223
a81=223

Answer 2

D=3; a81= -17+3 (81-1); а81= 233