If we have , and to be in A.P. then,
Then It should satisfy the condition,
[for a, b, c are in A.P]
Therefore,
LHS = RHS
Hence proved.
If we have , and to be in A.P. then,
Then It should satisfy the condition,
[for a, b, c are in A.P]
Therefore,
LHS = RHS
Hence proved.