Answer
$$ -16x^6+x^2-10x+25$$
Work Step by Step
Simplifying the expression using the fact that this is a difference of two squares, we find:
$$ \left(\left(x-5\right)-4x^3\right)\left(\left(x-5\right)+4x^3\right) \\ \left(x-5\right)^2-\left(4x^3\right)^2\\ -16x^6+x^2-10x+25$$
