#### Answer

$5x^n(3x^n-5)$

#### Work Step by Step

The greatest number that divides the numerical coefficients is 5.
The variable raised to the smallest exponent is $x^{n}$
Thus, the greatest common factor is $5x^{n}$.
Factor this out to obtain:
$15x^{2n}-25x^n=5x^n(3x^n-5)$