Question 873961
The reason for the 2x comes from expanding out  (x-1)^2


When you expand out  (x-1)^2, you will NOT get x^2 + 1


That's a very common fallacy people fall for.


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Here is what you should get


(x-1)^2 = (x-1)*(x-1)


(x-1)^2 = x(x-1) - 1(x-1)


(x-1)^2 = x^2 - x - x + 1


(x-1)^2 = x^2 - 2x + 1


I recommend using a rectangle to help multiply (example of what I mean shown below. In the example, they are multiplying out {{{(x+3)(x-2)}}})


<img src = "http://www.shelovesmath.com/wp-content/uploads/2012/10/Multiplication-Box-Method.png">

(Image Source: <a href="http://www.shelovesmath.com/algebra/intermediate-algebra/introduction-to-polynomials/">http://www.shelovesmath.com/algebra/intermediate-algebra/introduction-to-polynomials/</a>)