Check to see if two vectors are parallel

Question

This is a small excercise from Lang's Introduction to Linear Algebra

Two vectors $\overrightarrow{PQ}$ and $\overrightarrow{AB}$ are defined by these following n-tuples:
$P=(1,4), Q=(-3,5), A=(5,7), B=(9,6)$

I know that two vectors are parallel if $B-A=c(P-Q).$ If $c$ is greater than zero, then two vectors point at the same direction, while if c is smaller than zero, then they point at the opposite direction.

However, I fail to see how these two vectors are parallel. Computing $B-A=c(P-Q)$, we have:
$(B-A)=(4,-1)$ and $(P-Q)=(-4,1)$. How can these two vectors parallel?

The answer in the back of the book says they are parallel.

Answer 1

$(4,-1) = (-1) \ (-4,1)$

$-1$ is a scalar constant less than zero.