$P=P_{0}\left\{1-\frac{1}{2}\left(\frac{V_{0}}{V}\right)^{2}\right\} \quad ; \quad P V=n R T=R T$

$P=\frac{R T}{V}$

$\frac{R T}{V}=P_{0}\left\{1-\frac{V_{0}^{2}}{2 V^{2}}\right\}$

$T=\frac{P_{0} V}{R}\left\{1-\frac{V^{2}}{2 V^{2}}\right\}=\frac{P_{0}}{R}\left\{V-\frac{V_{0}^{2}}{2 V}\right\}$

$\Delta T $$=\frac{P_{0}}{R}\left\{\left(2 V_{0}-V_{0}\right)-\frac{V_{0}^{2}}{2}\left(\frac{1}{2 V_{0}}-\frac{1}{V_{0}}\right)\right\}$

$=\frac{P_{0}}{R}\left\{V_{0}-\frac{V_{0}^{2}}{2}\right\} $

$ \Delta T $$=\frac{P_{0}}{R}\left\{\left(2 V_{0}-V_{0}\right)-\frac{V_{0}^{2}}{2}\left(\frac{1}{2 V_{0}}-\frac{1}{V_{0}}\right)\right\} $

$=\frac{P_{0}}{R}\left\{V_{0}-\frac{V_{0}^{2}(1-2)}{2 \times 2 V_{0}}\right\} $

$=\frac{P_{0}}{R}\left\{V_{0}-\frac{V_{0}}{4}\right\}=\frac{3}{4} \frac{P_{0} V_{0}}{R}$