Question

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

Answer 1

Sum f(k)=4k-10  for k=1 to 18.

We sum each term separately and add the sums.

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

Therefore the required sum is 684-180=504

Answer 2

-6
-2
2
6
10
14
18
22
26
30
34
38
42
46
50
54
58
62
the sum is 504