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The sum of the first n terms of a linear sequence is \(S_{n}...

The sum of the first n terms of a linear sequence is Sn=n2+2n. Find the common difference of the sequence

A.

5

B.

4

C.

3

D.

2

Correct answer is D

Sn=n2(2a+(n1)d

n2(2a+(n1)d=n2+2n

n(2a+(n1)d=2n2+4n

2an+n2dnd=2n2+4n

Comparing the equations, d = 2 (coefficient of n2).