Write an equation of the line perpendicular to the graph of x=3 and passing through D(4, -1)

Question

I am completely stumped on this question and would really appreciate if someone could explain this for me! 

Answer 1

Since x = 3 is a vertical line, a horizontal line would be perpendicular to x = 3. Since the line must pass through (4,-1), the equation would be y = -1.