(a,b)²=(a²-b²,2ab)
(a,b,c)²=(a²-b²-c²,2ab,2ac,2bc)
(a,b,c)+(d,e)
=[(a,b),c]+(d,e)
=[(a,b)+d,c+e]
=[(a+d,b),c+e]
=(a+d,b,c+e)
