Question

Encontre a soma dos 30 primeiros termos da PA (3,7,11...)

Answer 1

S= (a¹+an) . n  / 2

An= a¹+ (n-1) .r

An= 3 + 29 . 4

An = 119

S= (3+119) . 30 / 2

S = 122 . 30 / 2     _ > 3660 / 2     _ > S = 1830

Answer 2

P.A (3,7,11,15,19,23,27,31,35,39,43,47,51,55,59,63,67,71,75,79,83,87,91,95,99,103,107,111,115,119) soma da P.A = 1830 obrigada