Which of the following is an equation of a vertical line?

Question

1) -4=16x

2) 4x+5y=-1

3) 3y=-9

4) 4x+5y=0

Answer 1

Since equation 1 can be written as x = -1/4, and vertical lines are always of the form x = k, where k is any real constant, equation 1 is our answer.

Answer 2

A vertical line has only a constant x value.