\(T_1=2\pi\sqrt{\dfrac{l_1}{g}};T_2=2\pi\sqrt{\dfrac{l_1\left[1+\alpha\left(t-t_0\right)\right]}{g}}\)
\(\Rightarrow\dfrac{T_1}{T_2}=\sqrt{\dfrac{l_1}{l_1\left[1+\alpha\left(t-t_0\right)\right]}}=\sqrt{\dfrac{1}{1+1,2.10^{-5}.25}}\Rightarrow T_2=\dfrac{9,8}{\sqrt{\dfrac{1}{1+1,2.25.10^{-5}}}}=...\left(s\right)\)