Answers

2015-02-08T13:07:13+05:30
Sn=n/2(a+xn)
xn=a+(n-1)d
sn=n/2[a+a+(n-1)d]
sn=n/2[2a+(n-1)d]



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2015-02-08T15:11:56+05:30
Sn=n/2(a+an)
sn=a+(n-1)d
sn=n/2[a+a+(n-1)d]
sn=n/2[2a+(n-1)d]
0