Valor Absoluto

$$|a|= \{{^{a; \text{ si a } \geq 0}_{-a; \text{ si a } < 0}}$$

$$|a|=|-a| $$

$$|a| \geq 0 $$

$$|ab|=|a||b|$$

$$|\frac{a}{b}| = \frac{|a|}{|b|}$$

$$|a+b|\leq |a|+|b|$$