Question 1039238
{{{a[4] = 16xy^4}}} and {{{a[1] = 2xy}}}  ==> {{{r^3 = 8y^3}}} ==> r = 2y.

==> The two geometric means are {{{a[2] = 2xy*2y = 4xy^2}}} and {{{a[3] = 4xy^2*2y = 8xy^3}}}