How to find the sum of the first 14 terms of the arithmetic sequence a_5 =6, a_7=10?

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Answer 1 · 2018-04-19T02:18:50

#154#

Find the common difference, which is #2# in this case

#a_7= a_5+d(7-5)#

#10= 6+d(2)#

#d=2#

Find #a_1#
#a_1= 6+2(1-5)= -2#

Find #a_14#
#a_14= 6+2(14-5)= 24#

Find Sum
#S_14= 14/2(-2+24)=154#