The sum of n terms of an ap is 3n2+5n. Find the ap .hence find the 15t

1.	The sum of n terms of an ap is 3n2+5n. Find the ap .hence find the 15th term
Answer» Given : Sn\xa0= 3n2\xa0+ 5nPut n = 1, we get sum of first 1 term i.e first term itself.S1 = a = 3(1)2 5(1) = 3 + 5 = 8So first term is 8.Put n = 2, we get sum of first 2 terms.\xa0S2\xa0= 3(2)2\xa0+ 5(2) = 12+10 = 22Second term =\xa0{tex}S_2 - S_1 = 22 - 8 = 14 {/tex}Common Difference = second term - first term = 14 - 8 = 6\xa0So AP = 8,14,20,26{tex}A_{15} = 8 + 14(6) = 8 + 84 = 92{/tex}\xa0

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