Question

dada a pa 10,14,18 calcule o valor do 20° termo e a soma da PA​

Answer 1

$> resolucao \\ \\ \geqslant progressao \: \: aritmetica \\ \\ r = a2 - a1 \\ r = 14 - 10 \\ r = 4 \\ \\ \\ a20 = a1 + 19r \\ a20 = 10 + 19 \times 4 \\ a20 = 10 + 76 \\ a20 = 86 \\ \\ = = = = = = = = = = = = = = = = = = = = = = = \\ \\ \\ > \: soma \: dos \: termos \: da \: pa \\ \\ sn = \frac{(a1 + an)n}{2} \\ \\ sn = \frac{(10 + 86)20}{2} \\ \\ sn = \frac{96 \times 20}{2} \\ \\ sn = 96 \times 10 \\ \\ sn = 960 \\ \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant \geqslant$