Answers

2016-06-28T14:14:26+08:00
1.) 1,3,5,7,9.......99 ( I didn't get your question in #1) 2.)Sn=n/2(a1+an) Sn= 14/2(1+53) Sn=7(54) Sn=378 3.)Sn=n/2(a1 + an) 530=10/2(a1 +80) 530=5(a1+80) 530=5a1+ 400 530-400=5a1 130=5a1 26= a1 (a1 read's as a sub 1) an=a1+(n-1)d 80=26+(10-1)d 80=26+(9)d 80-26=9d 54=9d 6=d (d is the common difference)
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