# What is the domain and range of y= -1?

Range = $\left\{- 1\right\}$
The domain is how much the function takes x-wise, in the horizontal axis. As $y = - 1$ is a horizontal line at $y = - 1$, horizontally-wise it takes all real numbers, from -∞ to  +∞ Therefore, the domain is ℝ.
The range is how much the function takes y-wise, in the horizontal axis. As $y = - 1$ is a horizontal line at $y = - 1$, vertically-wise it takes only -1. Therefore, the range is $\left\{- 1\right\}$