(2.3m^2+1.5n^2)^2
(2.3m^2+1.5n^2)^2 =
(2.3m^2+1.5n^2) (2.3m^2+1.5n^2) =
5.29m^4 + 6.9(m^2*n^2) + 2.25n^4