The common difference of an A.P., the sum of whose n terms is Sn, is
A. Sn – 2Sn–1 + Sn–2
B. Sn – 2Sn–1– Sn–2
C. Sn – Sn–2
D. Sn – Sn–1
an is the nth term of an A.P and an–1 is the (n–1)th term of an A.P,
d = common difference,
Sn = sum of n terms of an A.P
d= an – an–1
But an= Sn – Sn–1
And an–1= Sn–1 – Sn–2
So d= Sn – Sn–1 – ( Sn–1 – Sn–2)
d= Sn – 2 Sn–1 + Sn–2