Question

What is the slope of a line y=2?

Answer 1

`y=2` is a vertical line equation so the slope is `0`

One way to think about this is to remember the secant (slope between two points on a line) is given by
`m = (Delta y)/(Delta x)`
where `Delta y` means the change in `y` (for some change in `x`, i.e. `Delta x`).
Since `y` is a constant, the change in `y` (`Delta y`) is always going to be `0`.

Another way is to consider the slope-intercept equation for a straight line:
`y = mx + b`
Written in this form `m` is the slope (and `b` is the y-intercept)
`y=2`
is equivalent to `y= (0)x +2`
So the slope is `m=0`
(and the y-intercept is `y=2`).