Khan/khan-exercises — Issue #12797: Factoring difference of squares 2 - Factor out the 9?
Author: KhanBugz
Created: 2012-02-01 14:09:35+00:00
State: open
Labels: ie8, win7, wrong-or-unclear

Reporter: ajsoley@hotmail.com

Factoring 81x^2−9 as 9(3x-1)(3x+1) was graded as incorrect. It's not.

[factoring_difference_of_squares_2.html?seed=94&problem=0](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/factoring_difference_of_squares_2.html?seed=94&problem=0&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/factoring_difference_of_squares_2.html?seed=94&problem=0&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5B%5C%229(3x-1\)(3x%2B1\)%5C%22%5D%22%2C35%5D%2C%5B%22correct-activity%22%2C%22%5B%5C%22(9x-3\)(9x%2B3\)%5C%22%5D%22%2C14%5D%5D)

[["9(3x-1)(3x+1)"],["(9x-3)(9x+3)"]]

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