I have the group L and subgroups h and K Hi everyone. Stuck on finding a counterexample on conjugating matrices-gym-plz.jpg. I have worked out that ghg^-1 is the 2x2 matrix of Hi everyone. Stuck on finding a counterexample on conjugating matrices-mattadaq.gif. ( where g is the matrix of L and h is the matrix of the subgroup H).

So now I am trying to give a counter-example to prove the subgroup H is not a normal subgroup of L. I can't seem to find one though. Could someone please help?