Khan/khan-exercises — Issue #11792: Domain of a function - Factorable Fraction
Author: KhanBugz
Created: 2012-01-21 20:50:24+00:00
State: open
Labels: firefox, win7, wrong-or-unclear

Reporter: cwjmkj@gmail.com

Was asked domain of f(x)=\frac{x+6}{(x+6)(x-9)}, and correct answer was x \in R | x \neq -6, x \neq 9, but the x+6 appears in the numerator as well, so really the function is only undefined at x = 9.

[domain_of_a_function.html?seed=170&problem=two-denom-simplify](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/domain_of_a_function.html?seed=170&problem=two-denom-simplify&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/domain_of_a_function.html?seed=170&problem=two-denom-simplify&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5C%22None%20of%20the%20above.%5C%22%22%2C65%5D%2C%5B%22correct-activity%22%2C%22%5C%22%3Ccode%20style%3D%5C%5C%5C%22display%3A%20none%3B%5C%5C%5C%22%3E%5C%5C%5C%5C%7B%20%5C%5C%5C%5C%2C%20x%20%5C%5C%5C%5Cin%20%5C%5C%5C%5CRR%20%5C%5C%5C%5Cmid%20x%20%5C%5C%5C%5Cneq-6%2C%20%5C%5C%5C%5C%2Cx%20%5C%5C%5C%5Cneq9%5C%5C%5C%5C%2C%20%5C%5C%5C%5C%7D%3C%2Fcode%3E%5C%22%22%2C4%5D%5D)

["None of the above.","\\{ \\, x \\in \\RR \\mid x \\neq-6, \\,x \\neq9\\, \\}"]

Mozilla/5.0 (Windows NT 6.1; WOW64; rv:8.0) Gecko/20100101 Firefox/8.0

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