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प्रश्न
Find S2 for the A.P. 3,5,7,9,......
उत्तर
A.P. 3,5,7,9
Here, a = 3
d = t2 - t1 = 5 - 3
d = 2
Sn = `"n"/2[2"a" + ("n"-1)"d"]`
`"S"_2 = 2/2[2(3) + (2-1)2]`
= [6 + 1(2)]
= 6 + 2
= 8
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