Khan/khan-exercises — Issue #11793: Domain of a function - Factorable Fraction, again
Author: KhanBugz
Created: 2012-01-21 20:56:10+00:00
State: open
Labels: firefox, win7, wrong-or-unclear

Reporter: cwjmkj@gmail.com

Was asked domain of f(x) = \left{ \begin{array}{l} \frac{x+5}{(x+5)(x-8)} for x \neq 6 \\ 5 for x=6 \end{array}. Was told that x \in \\R | x \neq -5, x \neq 8, when in fact, the x+5 appears in both numerator and denominator, so cancels.

[domain_of_a_function.html?seed=182&problem=two-denom-cond-weird](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/domain_of_a_function.html?seed=182&problem=two-denom-cond-weird&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/domain_of_a_function.html?seed=182&problem=two-denom-cond-weird&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5C%22None%20of%20the%20above.%5C%22%22%2C23%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-5%2C%20%5C%5C%5C%5C%2Cx%20%5C%5C%5C%5Cneq8%5C%5C%5C%5C%2C%20%5C%5C%5C%5C%7D%3C%2Fcode%3E%5C%22%22%2C5%5D%5D)

["None of the above.","\\{ \\, x \\in \\RR \\mid x \\neq-5, \\,x \\neq8\\, \\}"]

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

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