An ideal gas is initially at temperature T and volume V. Its volume is increased by ΔV due to an increase in temperature ∆T , pressure remaining constant. The quantity δ=ΔV/(VΔT)

From ideal gas equation PV = RT    ....(i)PΔV=RΔT.......(ii)Dividing equation (ii) by (i) we getΔVV=ΔTT⇒ΔVVΔT=1T=δ ∴δ=1T. So the graph between δ and T will be rectangular hyperbola.