2019-01-18 22:34:12 +0100 received badge ● Famous Question (source) 2016-07-22 03:00:35 +0100 received badge ● Notable Question (source) 2015-12-17 15:18:43 +0100 received badge ● Popular Question (source) 2015-03-26 16:14:39 +0100 received badge ● Popular Question (source) 2015-03-26 16:14:39 +0100 received badge ● Notable Question (source) 2015-01-19 22:00:57 +0100 received badge ● Nice Question (source) 2015-01-17 13:23:39 +0100 received badge ● Student (source) 2015-01-15 07:42:14 +0100 asked a question what does ratpoly. = PolynomialRing(QQ) mean In official tutorial, I see the following command: ratpoly. = PolynomialRing(QQ)  I have python backgroud. I wonder what does it do and how it is implemented. After all, variable ratpoly is not defined previously. 2015-01-15 07:38:12 +0100 received badge ● Scholar (source) 2015-01-14 06:27:28 +0100 commented answer why don't sage return exact value in some functions so is it possible to get a (z-sqrt(2))*(z+sqrt(2))? 2015-01-14 04:33:00 +0100 received badge ● Editor (source) 2015-01-14 04:31:08 +0100 asked a question why don't sage return exact value in some functions Look at the following code: realpoly. = PolynomialRing(RR) factor(z^2-2)  it returns: (z - 1.41421356237310) * (z + 1.41421356237310)  why don't sage return (z-sqrt(2))*(z+sqrt(2))  and how can i make it to do that?