Khan/khan-exercises — pull request #78830 by chris-torrence (2013-09-22 03:18:43+00:00)
Title: Improve hints for domain problems with rational expressions

Several recent issues have reported bugs with this exercise: #75297, #71661, #71595. Improve the hints for the 3 problems with rational expressions, to make it clear that this isn't a "bug" but is just the definition of the domain of a function.