If two complex numbers are equal, a+bi=c+dia + bi = c + dia+bi=c+di, which of the following must be true?
a=ca = ca=c and b=db = db=d
a=da = da=d and b=cb = cb=c
a+b=c+da + b = c + da+b=c+d
a2+b2=c2+d2a^2 + b^2 = c^2 + d^2a2+b2=c2+d2