Theory Subtraction: (a+bi)−(c+di)=(a−c)+(b−d)i(a+bi)-(c+di)=(a-c)+(b-d)i(a+bi)−(c+di)=(a−c)+(b−d)i. If A+iB=C+iDA+iB=C+iDA+iB=C+iD, then A=CA=CA=C and B=DB=DB=D.