If sn the sum of first n terms of an ap is given by sn- 4n-n2 then find its nth terms and the common difference
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S1 = sum of one term = first term = 4*1 - 1^2
= 4 - 1
= 3
t1 = 3
S2 = sum of first two terms = t1 + t2 = 4*2 - 2^2
= 8 - 4
= 4
t2 = 4 - t1 = 4 - 3 = 1
so first term of AP = a = 4
cd = t2 - t1 = 1 - 4 = -3
nth term = tn = a + (n - 1) d
= 4 + (n - 1) (-3)
= 4 - 3n + 3
= 7 - 3n
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