性质 实数的绝对值有如下一些性质:
1、$\left| a \right| = \left| -a \right| \ge 0$;当且仅当$a=0$时有$\left| a \right|=0$
2、$-\left| a \right\| \le a \le \left| a \right|$
3、$\left| a \right| < h \Leftrightarrow -h < a < h$;$\left| a \right| \le h \Leftrightarrow -h \le a \le h \left( h>0 \right)$
4、对于任何$a$、$b \in R$,有如下的三角形不等式:
$$\left| a \right| - \left| b \right| \le \left| a \pm b \right| \le \left| a \right| + \left| b \right|$$
5、$\left| ab \right| = \left| a \right|\left| b \right|$
6、$\left| \frac{a}{b} \right| = \frac{\left| a \right|}{\left| b \right|}\left( b \ne 0 \right)$