joseygarridooydqdg joseygarridooydqdg
  • 15-05-2018
  • Mathematics
contestada

what is the sum of the arithmetic sequence 3,9,15...if there are 24 terms?

1) 2,028
2) 1,452
3) 1,1728
4) 2,268

Respuesta :

gmany
gmany gmany
  • 15-05-2018
[tex]a_1=3;\ a_2=9;\ a_3=15;\ ...\\\\d=a_2-a_1\to d=9-3=6[/tex]

The formula of the sum of the arithmetic sequence:

[tex]S_n=\dfrac{2a_1+(n-1)d}{2}cdot n[/tex]

Substitute:

[tex]a_1=3;\ d=6;\ n=24\\\\S_{24}=\dfrac{2\cdot3+(24-1)\cdot6}{2}\cdot24=(6+23\cdot6)\cdot12=(6+138)\cdot12=144\cdot12=1,728[/tex]

Answer: 1,728.
Answer Link
ansley556 ansley556
  • 09-05-2021

Answer:

1,728

Step-by-step explanation:

Answer Link

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