The sum of the first n terms of an AP is given by Sn=3n^2+6n.find the nth term of this AP
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Sn = 3n²+6n
S1 = a1 = 3 + 6 = 9
S2 = 3X4 + 6X2 = 24
a1 + a2 = S2
therefore, a2 = 24 - 9 = 15
d = a2 - a1 = 15 - 9 = 6
an = a + (n-1)d = 9 +(n-1) 6 = 9 + 6n - 6 = 3 + 6n = 3(1+2n)
S1 = a1 = 3 + 6 = 9
S2 = 3X4 + 6X2 = 24
a1 + a2 = S2
therefore, a2 = 24 - 9 = 15
d = a2 - a1 = 15 - 9 = 6
an = a + (n-1)d = 9 +(n-1) 6 = 9 + 6n - 6 = 3 + 6n = 3(1+2n)
kaurishleen125:
i'm so sorry.... i did a calculation mistake
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