x=-3, this is a vertical line at x=-3. (because for x=-3 is the line with all real values of y, (-oo, +oo).
For lines to be perpendicular, their slope have to be negative reciprocals. Mathematiclly:
m1*m2=-1
The slope of a vertical is infinite so m2=-1/+oo=0. Which means that the perpendiular line has a slope of zero, it is a horizontal line.
Since there is a slope of 0, the point slope intercept form of the lines is:
y=k where k is the constant that is equal to the y value that the line must pass through, which in this case is -4. So the perpendicular line is:
y=-4
