Answer
$-2x+y=-3$
Work Step by Step
The result of exercise 31 tells us that ${\bf v}=\langle a,\ b \rangle$ is perpendicular to lines $ax+by=c$.
Here, ${\bf v}=\langle -2,\ 1 \rangle$ and the lines are $-2x+y=c.$
Since $P(-2,-7)$ is on the line, its coordinates satisfy the line equation
$\left\{\begin{array}{l}
-2(-2)+(-7)=c\\
c=-3
\end{array}\right.$
so the line equation is: $\quad -2x+y=-3$
To graph the line, use the given point and $(0,-3).$
