Answer: $-T^2 [\frac{\delta(G/T)}{\delta T}]_P$

It can be derived from the definition of Entropy and Gibbs free energy, that, $[\frac{\delta(G/T)}{\delta T}]_P = - \frac{\Delta H}{T_2}$

$\Longrightarrow \Delta H =-T^2 [\frac{\delta(G/T)}{\delta T}]_P$

This is one of the forms of Gibbs-Hemholtz equation.