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May 19th, 2018, 04:45 AM  #1 
Newbie Joined: May 2018 From: United States Posts: 2 Thanks: 0 Math Focus: Algebra  Polynomial Factoring Question
I am consistently getting answers that my book says are wrong, but only in terms of positive or negative signs, with every other thing composing my answer (parenthesis, exponents, coefficients and variables) being consistently correct. The following would be the best representation of what I mean My Answer: (Midway through problem after using AC to convert my trinomial to a 4 term polynomial) x²3xyxy+3y² 3y(yx)x(yx) (3yx)(yx) Book Answer (x−3y)(x−y) The only difference is that each term in parenthesis has the reversed value in terms of being positive or negative, but I do not understand the reasoning. I can see that I am missing somthing very simple, (unless both answers are correct) but I have no idea what it is 
May 19th, 2018, 05:23 AM  #2 
Math Team Joined: Jul 2011 From: Texas Posts: 2,755 Thanks: 1405 
both factorizations are correct ... $(x3y)(xy) = (1)(3yx) \cdot (1)(yx) = (1)(1) \cdot (3yx)(yx) = (1) \cdot (3yx)(yx) = (3yx)(yx)$ 
May 19th, 2018, 01:05 PM  #3 
Global Moderator Joined: May 2007 Posts: 6,526 Thanks: 588 
If you write it as 3y(yx)+x(xy), you will see that something has to change sign in order to combine. The choice is arbitrary. You chose one way and the book chose the other.


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