$$
\begin{eqnarray*}
\{x\}&=&\bigcap_{i=0}^{∞} [x,x+\frac{1}{n})\(x,y)&=&[x,y)-\{x\}\[x,y]&=&[x,y)+\{y\}\(x,y]&=&[x,y)+\{y\}-\{x\}\end{eqnarray*}$$\{x\}&=&\bigcap_{i=0}^{∞} [x,
$$
\begin{eqnarray*}
\{x\}&=&\bigcap_{i=0}^{∞} [x,x+\frac{1}{n})\(x,y)&=&[x,y)-\{x\}\[x,y]&=&[x,y)+\{y\}\(x,y]&=&[x,y)+\{y\}-\{x\}\end{eqnarray*}$$\{x\}&=&\bigcap_{i=0}^{∞} [x,