(a) Obtain an expression for electrostatic potential energy of a system of three charges q, 2 q and -3 q placed at the vertices of an equilateral…

a similar diagram with different order of charges

\[U=\frac{1}{4 \pi \epsilon_{0}} \cdot \frac{\mathrm{q}_{1} \mathrm{q}_{2}}{\mathrm{r}} \] \(\displaystyle U=\frac{1}{4 \pi \epsilon_{0}}\left[\frac{2 \mathrm{q}^{2}}{a}-\frac{6 \mathrm{q}^{2}}{a}-\frac{3 \mathrm{q}^{2}}{a}\right] U=\frac{1}{4 \pi \epsilon_{0}} \frac{\left(-7 \mathrm{q}^{2}\right)}{a}\)