Question

Calcule a soma dos 100 primeiros termos da p.a. (12,16...)

Answer 1

PA = {12,16}

R = A2 - A1
R = 16 - 12
R = 4

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An = A1 + (n - 1)*r
An = 12 + (100 - 1)*4
An = 12 + 99*4
An = 12 + 396
An = 408

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Sn = (A1 + An)n/2
S100 = ( 12 + 408)100/2
S100 = 420*100/2
S100 = 420*50
S100 = 21000


Resposta : S100 = 21000