Question

qual a soma dos 21 primeiros termos da Pa (0,4,8,12....)

Answer 1

A1 = 0 r = 4 n = 21 An = ? Sn = ? An = A1 + (n - 1) . r An = 0 + (21 - 1) . 4 An = 0 + 80 An = 80 Sn = (A1 + An).n/2 S21 = (0 + 80).21/2 S21 = 80 . 21/2 S21 = 1680/2 S21 = 840