a
$U_{1}=\frac{1}{2} C_{1} V_{0}^{2}$
$C_{1} V_{0}=\left(C_{1}+C_{2}\right) V$
$V=\frac{C_{1} V_{0}}{C_{1}+C_{2}}$
$\mathrm{U}_{2}=\frac{1}{2}\left(\mathrm{C}_{1}+\mathrm{C}_{2}\right) \frac{\mathrm{C}_{1}^{2} \mathrm{V}_{0}^{2}}{\left(\mathrm{C}_{1}+\mathrm{C}_{2}\right)^{2}}=\frac{1}{2} \frac{\mathrm{C}_{1}^{2} \mathrm{V}_{0}^{2}}{\left(\mathrm{C}_{1}+\mathrm{C}_{2}\right)}$
$\frac{U_{1}}{U_{2}}=\frac{1 / 2 C_{1} V_{0}^{2}}{1 / 2 \frac{C_{1}^{2} V_{0}^{2}}{\left(C_{1}+C_{2}\right)}}$
$\frac{U_{1}}{U_{2}}=\frac{C_{1}+C_{2}}{C_{1}}$
