#### Answer

$\color{blue}{(\frac{5}{3}x^2+3y)(\frac{5}{3}x^2-3y)}$

#### Work Step by Step

With $\frac{25}{9}x^4=(\frac{5}{3}x^2)^2$ and $9y^=(3y)^2$, the given binomial is equivalent to:
$=(\frac{5}{3}x^2)^2-(3y)^2$
Factor using the formula $a^2-b^2=(a+b)(a-b)$ with $a=\frac{5}{3}x^2$ and $b=3y$ to obtain:
$=\color{blue}{(\frac{5}{3}x^2+3y)(\frac{5}{3}x^2-3y)}$