The characteristic equation of an R-S flip-flop with activeHIGH

The characteristic equation of an R-S flip-flop with activeHIGH inputs is given by—

1. Q_{n + 1} = S + R.Q_n
2. Q_{n + 1} = S′ + R.Q_n
3. Q_{n + 1} = S + R′.Q_n
4. Q_{n + 1} = R.Q′_n + S.Q_n

The characteristic equation of an RS flip-flop with active-HIGH inputs is given by
Q_{n + 1} = S + R′Q_n