Equations written in slope-intercept form follow a specific format.
y= mx+ b
Here, m represents the slope and b the y-intercept of the line. Let's rewrite our equation a little bit so that it more closely resembles this format. This will make it easier to identify its features.
y=-1 ⇔ y= 0x+( -1)
We see above that the slope is 0 and the y-intercept is -1.