In an A.P,the sum of its first n term is 6n-n².Find its 25th term
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Given,Sn = 3n2 + 4n
S1 = 3×1 + 4×1 = 7
S2 = 3×4 + 4×2 = 12 + 8 = 20.
Therefore, First term ,a1 = 7
& Second term a2 = 20 - 7 = 13
and d = 13 - 7 =6.
So,25th term, a25= 7 + ( 25 - 1) 6
a25 = 7 + 24 x 6
a25 = 151.
S1 = 3×1 + 4×1 = 7
S2 = 3×4 + 4×2 = 12 + 8 = 20.
Therefore, First term ,a1 = 7
& Second term a2 = 20 - 7 = 13
and d = 13 - 7 =6.
So,25th term, a25= 7 + ( 25 - 1) 6
a25 = 7 + 24 x 6
a25 = 151.
GauravKumarRai:
wrong answer
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