Minimizing X in Polyprotic Acids and Bases

[Sarah Giovennella 1G]

In polyprotic acids and bases (not including H2SO4) does the same rule apply that when the Ka or Kb values < 10^-4 we can minimize the value of X in the equilibrium expression to simplify the process of solving for X (and not having to use the quadratic formula)?

[SandraChane_1B]

Yes, I believe this applies to all acids and bases. It's also important to keep in mind the 5% ionization rule too.