You can put this solution on YOUR website! This is a special case. Anytime you have x=k, where k is a real number and there's no y, you have a vertical line going through k.
I can't graph vertical lines using this program. This is a vertical line going through 4:
X = 4
Draw your axese
Make a vertical line going up and down through x=4.
Hope that helps.
Happy Calculating!!!