Let other two sides of rhombus are

$$x - y + \lambda = 0$$

and $$7x - y + \mu = 0$$

then $$O$$ is equidistant from $$AB$$ and $$DC$$ and from $$AD$$ and $$BC$$

$$\therefore$$ $$\left| { - 1 + 2 + 1} \right| = \left| { - 1 + 2 + \lambda } \right| \Rightarrow \lambda = - 3$$

and $$\left| { - 7 + 2 - 5} \right| = \left| { - 7 + 2 + \mu } \right| \Rightarrow \mu = 15$$

$$\therefore$$ Other two sides are $$x-y-3=0$$ and $$7x-y+15=0$$

On solving the equations of sides pairwise, we get

the vertices as $$\left( {{1 \over 3},{{ - 8} \over 3}} \right),\left( {1,2} \right),\left( {{{ - 7} \over 3},{{ - 4} \over 3}} \right),\left( { - 3, - 6} \right)$$