Question

if Sn. the sum of first n terms of an AP is given by Sn is equal to 5n^2+ 3n then find its and nth term and common difference

Answer 1

sn = 5n^2+3n
s1 = 27
s2 = 106
a1= s1 =27
a2 = s2- s1 = 106-27=79
D = a2-a1 = 79 - 27 = 52
an = 27 +(n-1)52
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