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Please help me with this problem on demonstrations.

By using Rolle's Theorem, show that $f(x)=x^{10}+ax-b\quad,\quad {\rm where}\;\; a,b\in \mathbb{R}$ has at most two real roots.

Thanks in advance.

Grettings

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    Now I understood, thanks. I could solve it with your suggestion, assuming at least 3 roots of $f(x)$ and apply Rolle Theorem could then obtain a contradiction to conclude that $f'(x)$ has more than one root when in fact it has only one. Thanks, served me well.2011-08-12

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Hint: How many real roots does f'(x) have?

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    That's what I meant "reductio ad absurdum," excuse me, not fluent in English.2011-08-12