(2x/3y)^2*(2y/3x )^3次方/ (1/4的xy)
=(2x/3y)^2*(2y/3x )^2*(2y/3x )/ (1/4的xy)
=(4/9)^2*(2y/3x )/ (1/4的xy)
=(16/81)*(2y/3x )/ (1/4的xy)
=(32y/243x)/ (1/4的xy)
=128/243x^2