**This question already has answers here**: How to look up a symbol or identify a letter from a math alphabet or other character? (18 answers) Closed 8 years ago.

```
\item Obtain the one-to-one function $f_1$ and $f_2$ by cutting the graph of $f$ at
a certain point ($x_1$, $y_1$) so that domain of ($f_1$)=($-∞$ , $x_1$] and
domain ($f_2$)=[$x_1$,$+∞$)
```

A better style is:

Obtain the one-to-one function $f_1$ and $f_2$ by cutting the graph of $f$ at a certain point $(x_1, y_1)$ so that domain of $(f_1)=(-\infty , x_1]$ and domain $(f_2)=[x_1,+\infty)$

(Please compare the obtained spacing).