Find the sum of first 15 term having nth term as An= 3+4n
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63 is the correct answer
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AP is 7,11,15...
Common difference is 4
a = 7
So, S 15 = 15/2 [2a + (n-1)d} = 15/2 [ 14 + 14(7)] = 15/2 [14 x 8] = 840
Sum of 15 terms = 840
Common difference is 4
a = 7
So, S 15 = 15/2 [2a + (n-1)d} = 15/2 [ 14 + 14(7)] = 15/2 [14 x 8] = 840
Sum of 15 terms = 840
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