If a, b,and c are in G.P. and x, y, respectively, be arithmetic means between a, b and b, c, then the value of ax+cyis
Find the sum of first n terms of the series 3+7+13+21+31+....
Or
If a b and c are in GP and x,y are the arithmetic means of a,b and b,c respectively. prove that ax+cy=2 and 1x+1y=2b.