9000101010

Determine whether the following two lines are identical, parallel, intersecting or skew. $$\begin{array}{rlrl}a:x& =t,& & \\ y& =-t,& & \\ z& =1-t;t\in \mathbb{R}& & \end{array}$$$$\begin{array}{rlrl}b:x& =-s,& & \\ y& =s,& & \\ z& =-1+s;s\in \mathbb{R}& & \end{array}$$