Answer:
[tex] \frac{ |a + x| }{2} - \frac{ |a - x| }{2} \\ \\ = \frac{ | - 2 - 6| }{2} - \frac{ | - 2 + 6| }{2} \\ \\ = \frac{ | - 8| }{2} - \frac{ |4| }{2} \\ \\ = \frac{8}{2} - \frac{4}{2} \\ \\ = 4 - 2 = 2[/tex]
