If n geometric means between a and b be G1,G2,....Gn and a geometric mean of a and b be G, then the true relation is
Here G=(ab)12 and G1=ar1,G2=ar2,.....Gn=arn
Therefore G1,G2,G3,....Gn=anr1+2+..+n=anrn(n+1)2
But arn+1=b⇒r=(ba)1(n+1)
Therefore, the required product is
an(ba)1(n+1).n(n+1)2
Note : It is a well known fact.