1. The problem statement, all variables and given/known data if ax2+2bx+c=0 and a1x2+2b1x+c1 have a common root and a/a1 ,b/b1 ,c/c1 are in A.P. show that a1,b1,c1 are in G.P. 2. Relevant equations 3. The attempt at a solution I know the mean formula of A.P. i.e. the middle term is the mean of the other two. any hints of which formula of G.P. to use and how to solve???