Question

08. Dada a PG (10, 40, ...), determine a soma dos 4 primeiros termos. a) 430 b) 800 c) 850 d) 834 e) 831​

Answer 1

$> \: resolucao \\ \\ \geqslant \: progressao \: \: geometrica \\ \\ a1 = 10 \\ a2 = 40 \\ n = 4 \\ q = \frac{a2}{a1} = \frac{40}{10} = 4 \\ \\ = = = = = = = = = = = = = = = = \\ \\ > \: soma \: dos \: quatro \: primeiros \\ termos \: da \: pg \\ \\ sn = \frac{a1(q {}^{n} - 1) }{q - 1} \\ \\ sn = \frac{10(4 {}^{4} - 1)}{4 - 1} \\ \\ sn = \frac{10(256 - 1)}{3} \\ \\ sn = \frac{10 \times 255}{3} \\ \\ sn = \frac{2550}{3} \\ \\ sn = 850 \\ \\ \\ resposta \: > \: \: letra \: ( \: \: \: c \: \: \: ) \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant$