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Q1. How to solve a Quartic Equation. There is an online calculator available (and many more similar) that gives the precise answers and also defines the method. Does anyone know what the source of this method is?

Q2. Given a Quartic Equation

$$ ax^4+bx^3+cx^2+dx+e=0\,, $$ what are the conditions for the existence of real roots of the above equation? Any reference material?

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    Plese see. http://mathworld.wolfram.com/DescartesSignRule.html.2012-03-02
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    You still haven't read [this paper](http://www.jstor.org/stable/2972804)? I notice that you asked [this](http://math.stackexchange.com/questions/92689) months ago...2012-04-14
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    See also: http://math.stackexchange.com/a/786/722012-05-02
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    http://math.stackexchange.com/users/21481/abhinav http://math.stackexchange.com/users/26124/abhinav Are both of these your account?2012-05-14

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