1a,1b, and 1c, are in A. P. show that : bc , ca and ab are also in A.P.
If 1a,1b,1c are in A.P., prove that: (i) b+ca,c+ab,a+bc are in A.P. (ii) a(b+c),b(c+a),c(a+b) are in A.P.