Khan/khan-exercises — Issue #13282: Factoring difference of squares 2 - Incomplete/Wrong answer
Author: KhanBugz
Created: 2012-02-07 18:42:32+00:00
State: open
Labels: firefox, win7, wrong-or-unclear

Reporter: mneill@fz.k12.mo.us

What were you trying to do when the problem occurred?

Factor 64x^2 - 36

What happened that you didn't expect?

To completely factor this polynomial, you must first factor out the GCF which is 4. The result is 4(4x+3)(4x-3). The module expects an answer of (8x+6)(8x-6). This is not completely factored and is very confusing to students.

Please provide any additional information below.

I believe the goal of this module should be for students to factor polynomials which also happen to be a difference of two squares. When factoring and giving the correct answer as I did above, the module reports your answer as wrong...This is confusing for students who are still learning to factor.

Mike Neill
Math Coordinator
FZSD
636-474-8339

Thank you for the incredible work you are doing with this site!!! If there is any way I can contribute to this site, please allow me to help!!!

[factoring_difference_of_squares_2.html?seed=23&problem=0](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/factoring_difference_of_squares_2.html?seed=23&problem=0&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/factoring_difference_of_squares_2.html?seed=23&problem=0&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5B%5C%229(3x%2B1\)(3x-1\)%5C%22%5D%22%2C50%5D%2C%5B%22hint-activity%22%2C%220%22%2C3%5D%2C%5B%22hint-activity%22%2C%220%22%2C4%5D%2C%5B%22hint-activity%22%2C%220%22%2C4%5D%2C%5B%22hint-activity%22%2C%220%22%2C4%5D%2C%5B%22hint-activity%22%2C%220%22%2C4%5D%5D)

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

Mozilla/5.0 (Windows NT 6.1; rv:10.0) Gecko/20100101 Firefox/10.0

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