[tex] > \: resolucao \\ \\ \geqslant \: progressao \: \: aritmetica \\ \\ r = a2 - a1 \\ r = 15 - 6 \\ r = 9 \\ \\ = = = = = = = = = = = = = = = \\ \\ > \: o \: oitavo \: termo \: da \: pa \\ \\ an = a1 + (n - 1)r \\ an = 6 + (8 - 1)9 \\ an = 6 + 7 \times 9 \\ an = 6 + 63 \\ an = 69 \\ \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant [/tex]