This topic focuses on determining the domain of functions that feature a square root of a linear function over another linear function, practicing how to represent the domain on a number line. There are questions that involve identifying the correct number line that represents the domain of given functions, testing understanding of constraints on variable values imposed by the square root and the denominator to avoid divisions by zero or negative values under the square root. Each function has a unique set of possible answers depicted on number lines, facilitating the visualization of domains.