Question

What does decartes rules of signs tell you about the real roots of the polynomial? -x^3+5x^2-5x-6=0

Answer 1

-x^3+5x^2-5x=6
-x((x-5)x+5)-6=0

Answer 2

As it stands

-+-- That's two sign changes. 2, or 0 positive Real roots

Switching to f(-x)

+++- That's one sign change. There MUST be one negative Real root.