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

1 Answer
Tom M.
Jun 25, 2018

#210x+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#

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