Question

Qual é a SOMA dos 13 primeiros termos da PA ( 20, 26 ......) ? *

Answer 1

Resposta:

56

Explicação passo a passo:

r = 26 - 20 = 6

$a_1_3=a_1+12r\\\\a_1_3=20+12.6\\\\a_1_3=20+72\\\\a_1_3=92\\\\S_1_3=\frac{(20+92)}{2} \\\\S_1_3=10+46\\\\A_1_3=56$