Solution :
The sides of parallelogram are $$x=2, \,x=3, \,y=1, \,y=5.$$

$$\therefore $$ Diagonal $$AC$$ is $$\frac{{y - 1}}{{5 - 1}} = \frac{{x - 2}}{{3 - 2}}\,\,{\text{or}}\,\,y = 4x - 7$$
Equation diagonal $$BD$$ is $$\frac{{x - 2}}{{3 - 2}} = \frac{{y - 5}}{{1 - 5}}\,\,{\text{or}}\,\,4x + y = 13$$