Khan/khan-exercises — pull request #17760 by mathiash (2012-03-28 09:29:11+00:00)
Title: Factoring polynomials 2 and with 2 variables: accept more solutions

accept solutions like -2(x-1)(x-2) as well as 2(1-x)(x-2) or 2(1-x)(2-x), etc.