Question

Calculer a soma dos primeiros 30 termos da P.A(5,20,35)?

Answer 1

$> \: resolucao \\ \\ \geqslant \: progressao \: \: aritmetica \\ \\ r = a2 - a1 \\ r = 20 - 5 \\ r = 15 \\ \\ \\ > \: o \: 30 \: termo \: da \: pa \\ \\ an = a1 + (n - 1)r \\ an = 5 + (30 - 1)15 \\ an = 5 + 29 \times 15 \\ an = 5 + 435 \\ an = 440 \\ \\ \\ = = = = = = = = = = = = = = = = = \\ \\ \\ > \: soma \: dos \: termos \: da \: pa \\ \\ sn = \frac{(a1 + an)n}{2} \\ \\ sn = \frac{(5 + 440)30}{2} \\ \\ sn = \frac{445 \times 30}{2} \\ \\ sn = 445 \times 15 \\ \\ sn = 6675 \\ \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant$