# Theory of Equation (Descarte's Rule of Sign)

Most of the people I see gets confused about this rule. This rule actually cannot determine the number of roots. Specifically, this rule determines the NUMBER OF MAXIMUM real positive or negative roots by checking the number of change of signs in f(x) and f(-x). The word MAXIMUM should be given emphasis.

For the people who don't know this rule: Check this link http://en.wikipedia.org/wiki/Descartes'ruleof_signs

Note by Saswata Dasgupta
5 years, 8 months ago

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Can you contribute to the wiki on Descartes Rule of Sign here on Brilliant ?

Thanks :)

- 5 years, 8 months ago

Sure, but can you tell me how can I contribute?

- 5 years, 8 months ago

It's simple really !

Just got to the link that I have provided, click on "edit this page" and add the content that you think is appropriate :)

- 5 years, 8 months ago

I think this rule also tells us about the complex roots.

- 5 years, 8 months ago

Obviously you can get the MAXIMUM number of complex roots by taking out the number of MAXIMUM real roots from the total roots

- 5 years, 8 months ago

Yes I've checked the wolfram. It also says this.

- 5 years, 8 months ago