Question

the sum of the first n terms of an AP is given by Sn=3n-4n.Determine the AP and the 12th term

Answer 1

Given S n = 3n 2 + 4n. S 1 = 3×1 + 4×1 = 7. S 2 = 3×4 + 4×2 = 12 + 8 = 20 7=1