what is the equation of a line that goes through point (4, 0) and has an undefined slope?

Answer 1

A vertical line has an undefined slope. It has a equation that looks like: x=A (where A is a constant). Every point on that line has an x-value of A.

If a vertical line goes through point (4,0), every point on that line has a value of 4. The equation is:

x = 4

Answer 2

You would write this as: x=4 since the slope is undefined along the y-axis.