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There appears to be something wrong with the example. Plugging it all together, mathematica says Q1(x1,y1) Q2(x2,y2) != Q(X,Y). I'm not sure how to do the composition with mathematica, and Pari-gp doesn't work with positive discriminants, so I'm unsure how to check what is wrong.

Secondly, it is hard to tell that there is a "-" in the example cube, I only noticed it after looking at the matrices.

It would be nice if the example cube only used positive integers, and had a negative discriminant for easy checking with pari-gp. PineDoors ( talk) 20:52, 31 January 2020 (UTC) reply

Can someone please clarify how the (a,b,c,d,e,f,g,h) of the cube relates to p,q,r,s, p',q',r',s' in the "Gauss composition of integer binary quadratic forms" section? Are they the same values? This information would also be helpful for fixing up the broken example. PineDoors ( talk) 20:55, 31 January 2020 (UTC) reply