Question 18964
Plot the points? or plot the lines?
It's most likely lines because if it said plot the points, it would give you an x value with the y value in the same question
Basically, when it saids y=-2 it means y remains as -2 no matter the x value. Even if if was (400,-2)
Then it's a horizontal line
{{{graph(300,200,-5,5,-5,5,0x-2)}}}
Now x=4 is a different story.
It isn't a function, but it has the same principles as y=-2
Basically, no matter the y value, X always remains 4
So, it's a vertical line crossing the X-axis as (4,0). 
Hope this helps!