Given:
The coordinates of point P, (x1, y1)=(4, -9).
The coordinates of point Q, (x2, y2)=(-1, -9).
The length of PQ can be calculated as,
[tex]\begin{gathered} PQ=\sqrt[]{(x2-x1)^2+(y2-y1)^2} \\ PQ=\sqrt[]{(-1-4)^2+(-9-(-9))^2} \\ PQ=\sqrt[]{(-5)^2+0} \\ PQ=\sqrt[]{5^2} \\ PQ=5 \end{gathered}[/tex]
Therefore, the length PQ
