Question

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

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