Are you good at manipulating?

Algebra Level 2

$x=\dfrac {a-b}{a+b} \quad,\quad y=\dfrac {b-c}{b+c}\quad,\quad z=\dfrac {c-a}{c+a}.$

If $x,y$ and $z$ satisfy the equations above, then express $\dfrac {(1+x)(1+y)(1+z)}{(1-x)(1-y)(1-z)}$

in terms of $a,b$ and $c$ .

(abc)^{2}

-1

1

None of the above.

0

abc