Answer
(a) $0$
(b) Yes.
Work Step by Step
(a) Given $\vec u=\langle 2,-6,5 \rangle$ and $\vec u=\langle 1,-\frac{1}{2},-1 \rangle$, by definition the dot product is given by $\vec u\cdot\vec v=2\times1-6\times(-\frac{1}{2})+5\times(-1)=0$
(b) Since $\vec u\cdot\vec v=0$, the two vectors are perpendicular to each other.
