Question

Parallel, orthogonal, or neither.

Answer 1

Vectors are orthogonal, when dot product $u\cdot v=0$

$u\cdot v=\langle-1,3\rangle\cdot\langle-9,-3\rangle=(-1)\cdot(-9)+3\cdot(-3)=9-9=0$

Vectors $u$ and $v$ are orthogonal.