What is complementary transformation as applied to electronics?

Answer 1

If you swap the input and ground of a circuit, the transfer function becomes 1 - H(s), if the original circuit's transfer function was H(s). If H(s) = Numerator(s) / Denominator(s), putting all terms over a common denominator gives:

1 - H(s) = ((Denominator(s) - Numerator(s))/Denominator(s).

Often this subtraction in the numerator produces in complex zeros, which can be desirable.