Which of the following are A.P. (i) 1,3,5,7,…
(ii) `pi,pi+e^(pi),pi+2e^(pi),"...."`
(iii) `a, a-b, a-2b,a-3b,"…."`

Explanation

(i) Here, 2nd term - 1st term = 3rd term - 2nd term `="…."`
`implies 3-1=5-3="..."=2,` which is a common difference.
(ii) Here, 2nd term - 1st term = 3rd term -2nd term` ="…."`
`implies (pi+e^(pi))-pi=(pi+2e^(pi))-(pi+e^(pi))="...."`
`" "=e^(pi),` which is a common difference.
(iii) Here, 2n term -1st term = 3rd term -2nd term ="...."
`implies (a-b)-a=(a-2b)-(a-b)="...."`
`" "=-b,` which is a common difference.