Chemistry problem

Show that the following equations represent redox reactions:

equation 1: Mg + H2SO4 → MgSO4 +H2
equation 2: 3Cu + 8HNO3→ 3 Cu(NO3)2 + 2NO + 4 H2O
equation 3: 2H2SO4 + Fe→ Fe(SO4) + SO2 + H2O
equation 4: 2HCL + Mg → MgCl2 + H2