effect of adding an inert gas to a reaction mixture at equilibrium

Addition of inert gas to a reaction mixture effects the equilibrium in two ways-
1.At constant P--It is found that volume is increased by adding an inert gas to the mixture at constant pressure.Because in this case the total pressure will remain constant, but the partial pressures of the reactants and products will decrease. This is because the total pressure now includes the pressure resulting from the inert gas. This has the effect of diluting the mixture and is similar to simply mechanically increasing the volume.
2.At constant V--Increasing the pressure by adding an inert gas at constant volume has no effect on equilibrium. This is because for the equilibrium the partial pressures of the reactants and products matters. Adding an inert component to a system at constant volume will change the total pressure but not the partial pressures of the compounds thus there will be no effect on equlibrium.