Find Dxy using the rules for finding derivatives.

= (5x^2-8) (9x^2-3x+5)

You can do foil method first, to make it easier and to avoid product rule,

y = 45x^4 - 15x³ + 25x² - 72x² + 24x - 40

Simplify like terms,

y = 45x^4 - 15x³ - 47x² + 24x - 40

Now, find derivative,

dy/dx = 180x³ - 45x² - 94x + 24