If A1, A2, A3,..., An are n numbers between a and b, such that a, A1, A2, A3,..., An, b are in A.P., then
If A1, A2, A3,...., An are n numbers between a and b, such that a, A1, A2, A3,..., An, b are in A.P., then the common difference of this A.P. is: