The trial wave function of a system is expanded as $\psi_{t}=c_{1} \phi_{1}+c_{2} \phi_{2}$. The matrix elements of the Hamiltonian are $\left\langle\phi_{1}\right| \widehat{H}\left|\phi_{1}\right\rangle=0 ;\left\langle\phi_{1}\right| \widehat{H}\left|\phi_{2}\right\rangle=2.0=\left\langle\phi_{2}\right| \widehat{H}\left|\phi_{1}\right\rangle$ and $\left\langle\phi_{2}\right| \widehat{H}\left|\phi_{2}\right\rangle=3.0$. The approximate ground-state energy of the system from the linear variational principle is