Question

dada a p.a tem a 1 = -9 e r=7. determine seus 6 primeiros termos e calcule a soma deles

Answer 1

-9, -2, 5, 12, 19, 26

 $S= \frac{(a1+an)n}{2} = \frac{(-9+26)6}{2} = \frac{17.6}{2} = 51$