jhchampagne5 jhchampagne5
  • 25-06-2018
  • Mathematics
contestada

Find the sum of a finite arithmetic sequence from n=1 to n=18, using the expression 4n-10

A. 56
B. 116
C. 504
D. 1,016

Respuesta :

mathmate
mathmate mathmate
  • 25-06-2018
Sum f(k)=4k-10  for k=1 to 18.

We sum each term separately and add the sums.

[tex]\sum_1^{18}4k=4\sum_1^{18}k=4[18(1+18)/2]=4*9*19=684[/tex]
[tex]\sum_1^{18}-10=-10\sum_1^{18}1=-10*18=-180[/tex]

Therefore the required sum is 684-180=504
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