Question

for each equation, tell whether its graph is a horizontal or vertical line.
y=-4

Answer 1

y=a
is a horizontal line (has a slope is zero)

x=b
is a vertical line (where the slope doesn't exist).

Answer 2

Slope is C, where

as the line goes 1 unit to the right, it also goes C units up (C can be negative to, in that case this means that the line is going C units down, right?)


So when y=0, the graph goes only right and left, not up or down. So the slope is zero.

Answer 3

when the line is horizontal, then, it doesn't go up r down, as x goes 1 unit to the right each time.
This means it increases by 0 units up,
and therefore the slope is zero.

when the line is vertical the graph is just not going right and left and all, so therefore the slope is Undefined in a vertical line. i ti s just inapplicable, there is no such a thing as a slope when the line is vertical.