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#### CaptainBlack

##### Well-known member

- Jan 26, 2012

- 890

**rayman**'s question from another place:

Could someone help me with this problem, I have no idea how to start with it

How many real roots does this polynomial have p(x)=x^4-x^3-1?

Clearly state the argument that explains the number of real roots.

Thank you for any help

Descartes rule of signs tells you this has exactly 1 positive root, and exactly 1 negative root, so it has two real roots.

CB

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