Answer
Not orthogonal
Work Step by Step
We know that $\langle u_1,u_2 \rangle \cdot \langle v_1,v_2\rangle$ is equal to $u_1v_1 +u_2v_2$. Thus, we find that the dot product of these two vectors is:
$$(3)(-1)+(15)(5)=72$$
The dot product is not zero, so the vectors are not orthogonal.
