Question

determine a soma dos 15 termos da pa (5,9,13,...)​

Answer 1

Resposta:

an=a1+(n-1).r

an=5+(15-1).4

an=5+14.4

an=5+56

an=61

sn=(a1+an).n/2

$s = \frac{(5 + 61) \times 15}{2} = \\ \frac{66 \times 15}{2} = \\ \frac{990}{2} = \\ 495$

soma = 495