source 2009.04.01 Bernstein--Lange compute XX = X1^2 compute A = 2 Y1^2 compute AA = A^2 compute U = 2 AA compute S = (X1+A)^2-XX-AA compute M = 3 XX + T1 compute X3 = M^2 - 2 S compute Y3 = M(S-X3)-U compute Z3 = 2 Y1 Z1 compute T3 = 2 U T1