Answers

2015-10-28T18:09:27+05:30
S= 1, 2, 3..., n
it is an AP with a=1 and d=1
S= n/2 (2a+(n-1) d)
=n/2 (2+(n-1))
=n/2 (n+1)
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Which term of 24,23×1÷4,22×1÷2,21×3÷4 is first negative term
as such no negative term but I think its 2nd one . m nt sure,, n sry if m wrong
n did u get ans of ur first que
yes
nd 2nd ques is of AP
2015-10-28T21:33:22+05:30
Sn=n÷2(2a+(n-1)d) is the formula
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