Horizontal line has a slope of zero because does not rise vertically.
The form that we have to use in this case is y=b because the slope is zero.
So I would say that the answer for this one is
Y=-1
And a vertical line has a undefined slope because it will go up infinitely.
And in this one we have to put the x-intercept.
So I would say that the answer for this one is x=-9
I hope you get it right :D
