Respuesta :

Answer:

Step-by-step explanation:

∑1 to 18  (5n-4)

a1=5×1-4=1

a2=5×2-4=6

a18=5×18-4=86

n=18

[tex]S_{n}=\frac{n}{2} (a1+an)\\S_{18}=\frac{18}{2} (1+86)=9 \times 87=783[/tex]

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