source 2012 Chuengsatiansup parameter minustwo assume minustwo = -2 compute P = Y1 Z1 compute 2P = 2 P compute S = Y1 + Z1 compute A = S^2 - P compute C = (A - 2P) S compute D = A (Z1 - Y1) compute E = 3 C - d X1 2P compute X3 = minustwo X1 D compute Y3 = (D - E) Z1 compute Z3 = (D + E) Y1