An unusual notation for vectors? This is, word for word, with no other relevant context, a problem I was given:

Given the point $P(3,-2,1)$, find the point $Q$ such that $\vec{PQ}=[-1~~2~~5]^T$.

The issue I have is not with the problem itself, but with the vector's notation. The coordinates are separated by spaces, and I'm not sure what to make of the superscript $T$. Is anyone here familiar with this notation? Does it differ from regular (i.e. $\vec{s}=(1,2,3)$) notation? If so, how?
 A: With matrices (vectors), some people use a comma to separate elements while others use a space--they mean the same thing as far as what I've come across. The superscript $T$ indicates the transpose of the matrix.
A: $\vec{PQ}=[-1~~2~~5]^T$ is just the usual vector $(-1,2,5)$. The T means transpose. They probably use that notation to distinguish vectors from points in $\mathbb{R}^3$.
A: Yes, all it means is that if $P$ has coordinates 
$$
P = \begin{bmatrix} 3 \\ -2 \\ 1 \end{bmatrix}
$$
and $Q$ has some coordinates 
$$
Q = \begin{bmatrix} x \\ y \\ z \end{bmatrix},
$$
then
$$
Q-P = \overset{\longrightarrow}{PQ} = \begin{bmatrix} -1 \\ 2 \\ 5 \end{bmatrix}.
$$
You can easily solve for $Q$ in this equation and find $x = 2$, $y = 0$ and $z = 6$. 
All the $^{\top}$ means is transposition of matrices, i.e. $\begin{bmatrix} x & y & z \end{bmatrix}^{\top} = \begin{bmatrix} x \\ y \\ z \end{bmatrix}$.
Hope that helps,
A: The superscript $T$ implies you need to take transpose. It means $\bar{PQ}$ is a column vector, being the transpose of the row vector $(-1,2,5)$, i.e.
$$\bar{PQ}=\left(\begin{array}{c}-1\\2\\5\end{array}\right)$$ 
