For an adiabatic change, the value of dPP  is equal to ….(dv=change in volume,  δ=Cp Cv )

in an adiabatic process relation between pressure P and volume V is PVδ=Constantdifferentiate above equation with respect to P dPdP.Vδ+P.dVdPδ=01.Vδ+P.δ.Vδ-1.dVdP=0 ⇒Vδ=-P.δ.Vδ-1.dVdP⇒Vδδ.Vδ-1.dV=-PdP ⇒Vδ-δ+1δ.dV=-PdPinvert the ratio ⇒-δ.dVV=dPP⇒dPP=-δ.dVV