Find the sum of arithmetic sequence x - 2, 4x, 7x + 2, ... to 12 terms. ?

1 Answer
Jun 25, 2018

210x+108210x+108

Explanation:

An arithmetic sequence has a common difference.

:.d=4x-(x-2)
=3x+2

The sum of the first n terms of an arithmetic series can be given by

S_n=n/2(2a+(n-1)d)

where a is the first term.

:.S_12=12/2(2(x-2)+11(3x+2))
=6(2x-4+33x+22)
=6(35x+18)
=210x+108