Question

POR FAVOR ME AJUDEM !!!! 50 PONTOS MELHOR RESPOSTA

Determine a soma dos 8 primeiros termos da PG (-4; +8; -16, ...)

Answer 1

$P.G.(-4;+8;-16;...)\\\\S_{n} = ?\\ a_{1} =-4\\q=2\\n=8\\ \\\\ S_{n} = \frac{ a_{1} *( q^{n}-1) }{q-1} \\\\\\ S_{n} = \frac{ -4 *( 2^{8}-1) }{2-1} \\\\ S_{n} = \frac{ -4 *( 256-1) }{1} \\\\ S_{n} = -4 *255 \\\\ S_{n} = -1020$