Question

Calcule a soma (Sn) dos 6 termos da PA (2,5,8,...)?

Answer 1

$> resolucao \\ \\ \geqslant progressao \: \: aritmetica \\ \\ r = a2 - a1 \\ r = 5 - 2 \\ r = 3 \\ \\ a6 = a1 + 5r \\ a6 = 2 + 5 \times 3 \\ a6 = 2 + 15 \\ a6 = 17 \\ \\ = = = = = = = = = = = = = = = = = = = = = \\ \\ sn = \frac{(a1 + an)n}{2} \\ \\ sn = \frac{(2 + 17)6}{2} \\ \\ sn = \frac{19 \times 6}{2} \\ \\ sn = 19 \times 3 \\ \\ sn = 57 \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant$