[tex] > \: resolucao \\ \\ \geqslant \: progressao \: \: aritmetica \\ \\ r = a2 - a1 \\ r = - 1 - ( - 3) \\ r = - 1 + 3 \\ r = 2 \\ \\ \\ a15 = a1 + 14r \\ a15 = - 3 + 14 \times 2 \\ a15 = - 3 + 28 \\ a15 = 25 \\ \\ = = = = = = = = = = = = = = = = = \\ \\ \\ > \: soma \: dos \: termos \: da \: pa \\ \\ sn = \frac{(a1 + an)n}{2} \\ \\ sn = \frac{( - 3 + 25)15}{2} \\ \\ sn = \frac{22 \times 15}{2} \\ \\ sn = 11 \times 15 \\ \\ sn = 165 \\ \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant \geqslant [/tex]
