If a,b,c are in arithmetic progression , then show that the following are in arithematic progression :-
1. b+c , c+a , a+b
2. a+3k , b+3k , c+3k
3. a\7k , b\7k , c\7k
4. b+c-a , c+a-b , a+b-c
If a,1b,c and 1p,q,1rform two arithmetic progression of the same common difference, then a, q, c are in A.P. if